Add golang

```console
root@fca9dc756358:/stackbrew/stackbrew# ./brew-cli --debug --no-namespace -b golang --targets golang git://github.com/infosiftr/stackbrew
2014-08-01 00:04:22,374 DEBUG Cloning repo_url=git://github.com/infosiftr/stackbrew, ref=golang
2014-08-01 00:04:22,376 DEBUG folder = /tmp/tmpqLVfdv
2014-08-01 00:04:22,376 DEBUG Cloning git://github.com/infosiftr/stackbrew into /tmp/tmpqLVfdv
2014-08-01 00:04:22,376 DEBUG Executing "git clone git://github.com/infosiftr/stackbrew ." in /tmp/tmpqLVfdv
Cloning into '.'...
remote: Counting objects: 1045, done.
remote: Compressing objects: 100% (479/479), done.
remote: Total 1045 (delta 581), reused 989 (delta 554)
Receiving objects: 100% (1045/1045), 154.80 KiB | 0 bytes/s, done.
Resolving deltas: 100% (581/581), done.
Checking connectivity... done.
2014-08-01 00:04:23,320 DEBUG Checkout ref:golang in /tmp/tmpqLVfdv
2014-08-01 00:04:23,320 DEBUG Executing "git checkout golang" in /tmp/tmpqLVfdv
Branch golang set up to track remote branch golang from origin.
Switched to a new branch 'golang'
2014-08-01 00:04:23,326 DEBUG latest: git://github.com/docker-library/golang@b1da3bfd55b470d1791cb32ca253a1d853b6a149 1.3

2014-08-01 00:04:23,326 DEBUG 1:      git://github.com/docker-library/golang@b1da3bfd55b470d1791cb32ca253a1d853b6a149 1.3

2014-08-01 00:04:23,326 DEBUG 1.3:    git://github.com/docker-library/golang@b1da3bfd55b470d1791cb32ca253a1d853b6a149 1.3

2014-08-01 00:04:23,326 DEBUG onbuild:     git://github.com/docker-library/golang@b1da3bfd55b470d1791cb32ca253a1d853b6a149 1.3/onbuild

2014-08-01 00:04:23,326 DEBUG 1-onbuild:   git://github.com/docker-library/golang@b1da3bfd55b470d1791cb32ca253a1d853b6a149 1.3/onbuild

2014-08-01 00:04:23,326 DEBUG 1.3-onbuild: git://github.com/docker-library/golang@b1da3bfd55b470d1791cb32ca253a1d853b6a149 1.3/onbuild

2014-08-01 00:04:23,326 DEBUG cross:     git://github.com/docker-library/golang@b1da3bfd55b470d1791cb32ca253a1d853b6a149 1.3/cross

2014-08-01 00:04:23,326 DEBUG 1-cross:   git://github.com/docker-library/golang@b1da3bfd55b470d1791cb32ca253a1d853b6a149 1.3/cross

2014-08-01 00:04:23,326 DEBUG 1.3-cross: git://github.com/docker-library/golang@b1da3bfd55b470d1791cb32ca253a1d853b6a149 1.3/cross

2014-08-01 00:04:23,327 DEBUG 1.2:   git://github.com/docker-library/golang@b1da3bfd55b470d1791cb32ca253a1d853b6a149 1.2.2

2014-08-01 00:04:23,327 DEBUG 1.2.2: git://github.com/docker-library/golang@b1da3bfd55b470d1791cb32ca253a1d853b6a149 1.2.2

2014-08-01 00:04:23,327 DEBUG 1.2-onbuild:   git://github.com/docker-library/golang@b1da3bfd55b470d1791cb32ca253a1d853b6a149 1.2.2/onbuild

2014-08-01 00:04:23,327 DEBUG 1.2.2-onbuild: git://github.com/docker-library/golang@b1da3bfd55b470d1791cb32ca253a1d853b6a149 1.2.2/onbuild

2014-08-01 00:04:23,327 DEBUG 1.2-cross:   git://github.com/docker-library/golang@b1da3bfd55b470d1791cb32ca253a1d853b6a149 1.2.2/cross

2014-08-01 00:04:23,327 DEBUG 1.2.2-cross: git://github.com/docker-library/golang@b1da3bfd55b470d1791cb32ca253a1d853b6a149 1.2.2/cross

2014-08-01 00:04:23,327 DEBUG golang: onbuild,1-onbuild,1.3-onbuild
2014-08-01 00:04:23,327 DEBUG golang: 1.2,1.2.2
2014-08-01 00:04:23,327 DEBUG golang: 1.2-onbuild,1.2.2-onbuild
2014-08-01 00:04:23,327 DEBUG golang: cross,1-cross,1.3-cross
2014-08-01 00:04:23,327 DEBUG golang: latest,1,1.3
2014-08-01 00:04:23,327 DEBUG golang: 1.2-cross,1.2.2-cross
2014-08-01 00:04:23,328 DEBUG Cloning repo_url=git://github.com/docker-library/golang, ref=b1da3bfd55b470d1791cb32ca253a1d853b6a149
2014-08-01 00:04:23,328 DEBUG folder = /tmp/tmpkhRnwp
2014-08-01 00:04:23,328 DEBUG Cloning git://github.com/docker-library/golang into /tmp/tmpkhRnwp
2014-08-01 00:04:23,328 DEBUG Executing "git clone git://github.com/docker-library/golang ." in /tmp/tmpkhRnwp
Cloning into '.'...
remote: Counting objects: 37, done.
remote: Compressing objects: 100% (19/19), done.
remote: Total 37 (delta 8), reused 36 (delta 7)
Receiving objects: 100% (37/37), 4.05 KiB | 0 bytes/s, done.
Resolving deltas: 100% (8/8), done.
Checking connectivity... done.
2014-08-01 00:04:23,798 DEBUG Checkout ref:b1da3bfd55b470d1791cb32ca253a1d853b6a149 in /tmp/tmpkhRnwp
2014-08-01 00:04:23,799 DEBUG Executing "git checkout b1da3bfd55b470d1791cb32ca253a1d853b6a149" in /tmp/tmpkhRnwp
Note: checking out 'b1da3bfd55b470d1791cb32ca253a1d853b6a149'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

  git checkout -b new_branch_name

HEAD is now at b1da3bf... Add a one-liner that provides a list of supported os/arch combos from within a Go source tree
2014-08-01 00:04:23,804 INFO Build start: golang ('git://github.com/docker-library/golang', 'b1da3bfd55b470d1791cb32ca253a1d853b6a149', '1.3/onbuild')
2014-08-01 00:04:25,161 INFO Build success: 2926b85ca457 (golang:onbuild)
2014-08-01 00:04:25,185 INFO Build success: 2926b85ca457 (golang:1-onbuild)
2014-08-01 00:04:25,200 INFO Build success: 2926b85ca457 (golang:1.3-onbuild)
2014-08-01 00:04:25,216 DEBUG Checkout ref:b1da3bfd55b470d1791cb32ca253a1d853b6a149 in /tmp/tmpkhRnwp
2014-08-01 00:04:25,216 DEBUG Executing "git checkout b1da3bfd55b470d1791cb32ca253a1d853b6a149" in /tmp/tmpkhRnwp
HEAD is now at b1da3bf... Add a one-liner that provides a list of supported os/arch combos from within a Go source tree
2014-08-01 00:04:25,221 INFO Build start: golang ('git://github.com/docker-library/golang', 'b1da3bfd55b470d1791cb32ca253a1d853b6a149', '1.2.2')
2014-08-01 00:04:27,231 INFO Build success: 7d1c2411c433 (golang:1.2)
2014-08-01 00:04:27,258 INFO Build success: 7d1c2411c433 (golang:1.2.2)
2014-08-01 00:04:27,267 DEBUG Checkout ref:b1da3bfd55b470d1791cb32ca253a1d853b6a149 in /tmp/tmpkhRnwp
2014-08-01 00:04:27,267 DEBUG Executing "git checkout b1da3bfd55b470d1791cb32ca253a1d853b6a149" in /tmp/tmpkhRnwp
HEAD is now at b1da3bf... Add a one-liner that provides a list of supported os/arch combos from within a Go source tree
2014-08-01 00:04:27,271 INFO Build start: golang ('git://github.com/docker-library/golang', 'b1da3bfd55b470d1791cb32ca253a1d853b6a149', '1.2.2/onbuild')
2014-08-01 00:04:28,573 INFO Build success: 38e4dcb39e5a (golang:1.2-onbuild)
2014-08-01 00:04:28,599 INFO Build success: 38e4dcb39e5a (golang:1.2.2-onbuild)
2014-08-01 00:04:28,611 DEBUG Checkout ref:b1da3bfd55b470d1791cb32ca253a1d853b6a149 in /tmp/tmpkhRnwp
2014-08-01 00:04:28,611 DEBUG Executing "git checkout b1da3bfd55b470d1791cb32ca253a1d853b6a149" in /tmp/tmpkhRnwp
HEAD is now at b1da3bf... Add a one-liner that provides a list of supported os/arch combos from within a Go source tree
2014-08-01 00:04:28,615 INFO Build start: golang ('git://github.com/docker-library/golang', 'b1da3bfd55b470d1791cb32ca253a1d853b6a149', '1.3/cross')
2014-08-01 00:04:29,297 INFO Build success: 14c1c7a7bd9c (golang:cross)
2014-08-01 00:04:29,313 INFO Build success: 14c1c7a7bd9c (golang:1-cross)
2014-08-01 00:04:29,322 INFO Build success: 14c1c7a7bd9c (golang:1.3-cross)
2014-08-01 00:04:29,332 DEBUG Checkout ref:b1da3bfd55b470d1791cb32ca253a1d853b6a149 in /tmp/tmpkhRnwp
2014-08-01 00:04:29,332 DEBUG Executing "git checkout b1da3bfd55b470d1791cb32ca253a1d853b6a149" in /tmp/tmpkhRnwp
HEAD is now at b1da3bf... Add a one-liner that provides a list of supported os/arch combos from within a Go source tree
2014-08-01 00:04:29,336 INFO Build start: golang ('git://github.com/docker-library/golang', 'b1da3bfd55b470d1791cb32ca253a1d853b6a149', '1.3')
2014-08-01 00:04:31,314 INFO Build success: 0a615b2ecb6f (golang:latest)
2014-08-01 00:04:31,346 INFO Build success: 0a615b2ecb6f (golang:1)
2014-08-01 00:04:31,357 INFO Build success: 0a615b2ecb6f (golang:1.3)
2014-08-01 00:04:31,380 DEBUG Checkout ref:b1da3bfd55b470d1791cb32ca253a1d853b6a149 in /tmp/tmpkhRnwp
2014-08-01 00:04:31,380 DEBUG Executing "git checkout b1da3bfd55b470d1791cb32ca253a1d853b6a149" in /tmp/tmpkhRnwp
HEAD is now at b1da3bf... Add a one-liner that provides a list of supported os/arch combos from within a Go source tree
2014-08-01 00:04:31,385 INFO Build start: golang ('git://github.com/docker-library/golang', 'b1da3bfd55b470d1791cb32ca253a1d853b6a149', '1.2.2/cross')
2014-08-01 00:04:32,060 INFO Build success: c6cb87ff804d (golang:1.2-cross)
2014-08-01 00:04:32,084 INFO Build success: c6cb87ff804d (golang:1.2.2-cross)
```
```console
root@fca9dc756358:/stackbrew/stackbrew# docker images golang
REPOSITORY          TAG                 IMAGE ID            CREATED             VIRTUAL SIZE
golang              1.2.2-cross         c6cb87ff804d        5 hours ago         1.785 GB
golang              1.2-cross           c6cb87ff804d        5 hours ago         1.785 GB
golang              1.2.2-onbuild       38e4dcb39e5a        5 hours ago         415.7 MB
golang              1.2-onbuild         38e4dcb39e5a        5 hours ago         415.7 MB
golang              1.2.2               7d1c2411c433        5 hours ago         415.7 MB
golang              1.2                 7d1c2411c433        5 hours ago         415.7 MB
golang              1.3-onbuild         2926b85ca457        5 hours ago         413.9 MB
golang              1-onbuild           2926b85ca457        5 hours ago         413.9 MB
golang              onbuild             2926b85ca457        5 hours ago         413.9 MB
golang              1.3-cross           14c1c7a7bd9c        5 hours ago         1.812 GB
golang              cross               14c1c7a7bd9c        5 hours ago         1.812 GB
golang              1-cross             14c1c7a7bd9c        5 hours ago         1.812 GB
golang              latest              0a615b2ecb6f        6 hours ago         413.9 MB
golang              1                   0a615b2ecb6f        6 hours ago         413.9 MB
golang              1.3                 0a615b2ecb6f        6 hours ago         413.9 MB
```

Closes #66