Issue #266 - Add assisted inject support

Contains 2 fairly simple changes:
- In InjectionPoint, check for injectable fields AND methods since computeInjectableMembers handles both
- In GuiceAnnotationProcessor, always output information about FactoryProvider2 to ensure injection of the initialize method.  I'm not sure that I've taken the best approach with this change because I've never worked with annotation processors.  Maybe there is a more type-safe way to get information about the class and it's method (rather than hard-coding the strings), but from my understanding the annotation processor is only provided information about the classes currently being compiled.

I don't _think_ I've introduced any checkstyle issues, but the build did fail due to violations although they appeared to be unrelated.  I would have liked to include some tests but testing an annotation processor seems difficult.  Lastly, I hope I'm submitting this to the right place, this is my first PR so go easy on me.