Merge pull request #31 from aheusingfeld/master

Fixed some bugs and updated version
Update readme with latest changes.
Switch to ConcurrentHashMap instead of manually locking.

Experienced deadlocks when using the plugin,
Original purpose of synchronized blocks was to prevent getting
  the same resource from the server twice if it wasn't necessary.
  However, duplicating get work is preferable to locking up IntelliJ.

In other words, concurrency is hard.
Update readme.
Update version to 1.0.6 in preparation for release.
Update version to 1.0.7-SNAPSHOT in preparation of more work.
Fix #32 - NPE when looking at non-sonar file.

ConcurrentHashMap doesn't support null keys/values.
Update to version 1.0.7 in preparation of release.
Update version to 1.0.8-SNAPSHOT in preparation of more work.
Fixed #33 "NPE during initial configuration"

* prevented potential NPE

Issues: #33
uploaded demo of bugfix #33