Merge remote-tracking branch 'upstream/master'

Conflicts:
    src/main/java/org/jenkinsci/plugins/ghprb/GhprbGitHub.java
    src/main/java/org/jenkinsci/plugins/ghprb/GhprbRepository.java
Merge pull request #1 from rightscale/merge_upstream

Merge remote-tracking branch 'upstream/master'