Can now specify a build target for fedora and distgit releasers

Tito only supported the default build target when releasing,
however, in some cases it was necessisary to change it (building
for zstream for example).

By default, the build target is the same as the branch. With this
change, you can specify a build target on a per branch basis by
adding a 'build_targets' property in the releasers.conf file.

This property takes on the following format:
   build_targets = <branch>:<build_target> <branch>:<build_target> ...

An example configuration could be:

[project-x.y.z]
releaser = tito.release.DistGitReleaser
branches = project-x.y
build_targets = project-x.y:project-x.y.z-candidate

Running:
    tito release project-x.y.z

would instruct the build system to build with the target
'project-x.y.z-candidate' when building from the project-x.y
branch (i.e rhpkg build --no-wait --target project-x.y.z-candidate).
Automatic commit of package [tito] release [0.4.9-1].
Add Fedora 18 releases.
Handle stderr noise getting from remote server

Use regular expression to extract the SHA1 from the `git ls-remote` call
response. The reason is that there might be some messages in the
response going to stderr, that are captured when using run_command,
e.g.:

```
Could not chdir to home directory /home/johndoe: No such file or directory
fe87e2b75ed1850718d99c797cc171b88bfad5ca refs/tags/my-awesome-lib-1.0.1-1
```

I used 30 and more characters for the regular expression because I was
not sure the SHA1 is always shown as 40 characters. However we can be
quite certain that the word of 30 and more [0-9a-f] characters is a
SHA1.
Merge pull request #50 from iNecas/extractsha1

Handle stderr noise getting from remote server
pass in arguments to builder
change args -> mock_args to be a bit clearer.
Merge pull request #51 from dgoodwin/builderarg

pass in arguments to builder
remove tabs and trailing whitespace. add whitespace between methods
fix: RsyncReleaser doesn't handle multiple rsync locations

The refactoring of YumRepoReleaser into RsyncReleaser and
YumRepoReleaser caused a regression that didn't allow multiple rsync
locations to be defined and sync'd properly.

Moved a bunch of code around and adding of method variables to
allow multiple rsync and tempdirs to be used.
pep8: cleanup common.py
Merge pull request #52 from dgoodwin/fixyumrepo

Fix YumRepoReleaser to sync to multiple targets
Merge pull request #46 from mstead/master

Added ability to specify build targets for DistGitReleaser and FedoraReleaser.
Update README.mkd

Add proper formating for the "releasing packages" section, so it appear correctly on github
Merge pull request #53 from mscherer/patch-1

Update README.mkd
Add a Travis configuration

Travis[1] runs continuous integration for Open Source projects. With
github, it will run the configured tests and tag pull requests as passing
or failing. This commit adds a Travis configuration.

Since Travis hosts run debian/ubuntu, and execute tests in virtualenv,
getting access to `rpm` and `python-rpm` is impossible, or nontrivial,
at least. For now, ignore the functional tests. To support running the
BuildTargetParser tests, pull that class out into its own module, and
away from release.py, which imports `rpm`.

To configure travis, go to the website, log in with your github account,
then sync your repos under the account tab below your name. Then just
switch the repo to 'on' and it should be all set up.

[1]: http://travis-ci.org
Merge pull request #55 from jbowes/travis

Add a Travis configuration