Test to verify JENKINS-20660 exists in current code

The test is not an exact duplication of the error scenario, but is close
enough to show the problem is resolved.  Exact duplication would require
that a job be defined without a RegExToKill defined, then that job would
need to be executed in a Jenkins instance with the new plugin.

Adds dependency on JUnit 4.11 and Hamcrest, modeled after the same
technique used in Jenkins core and in plugins like the Git plugin.
Fix JENKINS-20660 - null pointer exception on first run after upgrade 0.8 to 0.9
More active defenses against null regexToKill
Merge pull request #11 from MarkEWaite/JENKINS-20660

Fix JENKINS-20660 - null pointer exception on first run after upgrade 0.8 to 0.9