Update to sbt 0.13.2
Slight refactoring and small changes

  - Add shortBuildNumber
  - Add decoratedShortBuildNumber
  - Add branchName
  - Run git commands in baseDirectory
Add a simple README.
Remove JGit since we don't use it
Generalize SCM support
Add preliminary Mercurial support
Merge pull request #1 from hkroger/develop

Add preliminary Mercurial support
Remove whitespace
Add version
Merge branch 'release/0.0.1'