Clean pom, use checkstyle, findbugs and PMD

https://github.com/roboguice/roboguice/issues/165

@emmby, what do you think of such a setup. The builds by defaults check for checkstyle, pmd and findbugs. 

I tried to stick to your coding standards as much as possible.
I corrected a few bugs found by findbugs and added a few exceptions when I was not sure.

What do you think of it ?

BTW, did you receive my question on G+ ?