Merge pull request #13 from emsa23/master

Towards 2.5
[maven-release-plugin] prepare release PrioritySorter-2.5
[maven-release-plugin] prepare for next development iteration
[FIXED JENKINS-21310] CCE when a Queue.Task was not a Job.
Merge pull request #14 from jglick/CCE-JENKINS-21310

[FIXED JENKINS-21310] CCE when a Queue.Task was not a Job
[JENKINS-21316] PrioritySorter wrongly assumes Queue.Task is Job

 * Updated fix provided for [JENKINS-21310] to exit early
 * Updated javadoc to clearify responsibilities