JENKINS-13726: Support for GitHub Enterprise.
Drop snapshot.
Merge pull request #22 from johnou/enterprise

[FIXED JENKINS-13726] Github plugin should work with Github enterprise by allowing for overriding the github URL.
[maven-release-plugin] prepare release github-1.5
[maven-release-plugin] prepare for next development iteration
Merge git://github.com/jenkinsci/github-plugin