Project wide CS fix + minor improvements

Please ignore first commit that belongs to #186. If #186 is merge, I'll rebase this branch onto `videlalvaro:master` and only the last commit will remain.

In this PR, I read thru all the classes and improved the following:

 - CS fix / enforcement / consistency
 - Comment adding
 - Control structure complexity improvements
 - Type hinting enforcement
 - Code cleaning

There are major design issues in this lib and I would love helping out but my low level knowledge of AMQP are way to low. If I have some more time, I'll try to propose a new skeleton for a next major version that would avoid the current mess in static calls.

Reviews are very welcomed and please try the branch before merging since I couldn't test in with real working environment.

Thanks,
FYI, it's not in PSR