Add eclipse specific files to gitignore
Fix NPEs during MR checks

* The first NPE occurred when the _mergeRequestStatus was not set for the merge request wrapper
* The second NPE occured when the merge request wrapper was trying to determine whether a MR job should be invoked.
  MR on gitlab which are stalled would cause NPE's since the lastest commit could not be determined.
  The plugin will now skip the run for these MRs.
Improve plugin setup guide.
Merge pull request #73 from Jotschi/bugfix-issue-60

Bugfix issue 60