Add autorequire for Package['git']

If the git package is being managed, it stands to reason that the git
package should be installed before trying to potentially manage git
repositories using vcsrepo resources.

This commit adds an autorequire to the vcsrepo type that reflects the
above premise.
Merge pull request #98 from reidmv/autorequire_git

Add autorequire for Package['git']
Prepare 0.2.0 release.
Merge pull request #102 from apenney/020-release

Prepare 0.2.0 release.
origin/HEAD is not valid; use origin/master for latest when branch == 'master'
Using rev-parse to determine branch name of HEAD for on_branch? method
Merge pull request #106 from mikegerwitz/master

Correctly handle detached head for 'latest' on latest Git versions
Stripping git on_branch? return value; contains trailing newline

This commit also contains git provider `latest' method formatting changes;
squashed by request.
Merge pull request #109 from mikegerwitz/master

Bug fix: Git provider on_branch? retains trailing newline