patched Makefile to use prepackaged Google binary of go
patched Makefile to continue using build/go if it exists, otherwise we
try to use a release binary
added a check_goroot python script to look for go in some common directories
changed the GOBIN target to only attempt building the hg checkout of go if heka-build/build/go exists, otherwise, try using the google prepackaged go binary
updated check_goroot to make stricter checks for a GOROOT
got rid of trying to build go from source and always copy over the
latest go binary
Don't barf on non-digits in version string (e.g. "1.1rc3"), and use python's version
compare utilities.
Check heka-build directory for go installation.
`check_goroot.py` now either prints a >=1.1 GOROOT path, if it finds one, or nothing,
if not. `Makefile` now sets GOROOT and GOBIN values accordingly, errors out if this
can't be done.
Merge pull request #20 from mozilla-services/features/issue_180

patched Makefile to use prepackaged Google binary of go
subprocess.check_output wasn't introduced until python 2.7, use older spelling for
more compatibility.