title: Jenkins github pull request builder plugin is not posting to github
body: <p>I have configured the Jenkins Github Pull-Request builder plugin to build every pull-request made by members of my institution. It works like a charm. </p>
  
  <p>However, the build is not reporting the build status back to github like it shows in this nice <a href="http://blog.kabisa.nl/2013/11/05/building-github-pull-requests-with-jenkins/">post</a>. I also tried checking the box to "Use comments to report results when updating commit status fails", but still I get nothing back on github. </p>
  
  <p>I have created a bot user on GitHub and given it push and administrative rights to the repo. </p>
  
  <p>My Jenkins server is behind a firewall, but since it is building normally and detecting changes (by polling) to the github repo, I assume this is not the issue. </p>
  
  <p>Anyone else had this issue? How did you solve it? </p>
  
  <p>Here is a dump of my console output (compressed for readability)</p>
  
  <pre><code>Started by an SCM change
  Building in workspace 
  Fetching changes from the remote Git repository
  Fetching upstream changes from repo
  Seen branch in repository origin/HEAD
  Seen branch in repository origin/master
  Seen branch in repository origin/pr/1/head
  Seen branch in repository origin/pr/1/merge
  Seen branch in repository origin/pr/10/head
  […]
  Seen branch in repository origin/pr/9/head
  Seen branch in repository origin/pr/9/merge
  Seen 33 remote branches
  Checking out Revision 9b4d45ee3a2d265a1268c2931e7b2bcb738e1c87 (origin/pr/16/merge)
  First time build. Skipping changelog.
  ...found 160 targets...
  ...updating 21 targets...
  **passed** test/bin/test.test/gcc-4.8.1/debug/test.test
  [xUnit] [INFO] - Starting to record.
  [xUnit] [INFO] - Processing BoostTest-1.x (default)
  [xUnit] [INFO] - Check 'Failed Tests' threshold.
  [xUnit] [INFO] - Check 'Skipped Tests' threshold.
  [xUnit] [INFO] - Setting the build status to SUCCESS
  [xUnit] [INFO] - Stopping recording.
  Finished: SUCCESS
  </code></pre>