Add initialize method to JobPerformer.

@yauuie,

I was able to add an initialize method to JobPerformer, but I'd like to hear your thoughts about where to put the hook detection. Hook detection currently live in Plugin, its needed there for linting. Its used in Job as well to detect the hooks and pass them to JobPerformer.

This is my only idea of where to go from here:
* call out to Plugin from JobPerformer instead of Job
* move the hook detection into a module HookDetection or something
* both :)

Any thoughts?