improve handling of issue comment hook
refactoring and reformatting

Performed some much needed cleanup and refactoring of the code, including
documenting some of the existing classes.
Merge pull request #138 from valdisrigdon/cleanup

refactoring and reformatting
Merge remote-tracking branch 'upstream/pr/135'

Conflicts:
	src/main/java/org/jenkinsci/plugins/ghprb/GhprbRepository.java