Major touchup

* Added docblocks
* Added namespace
* Improved composer configuration
* Streamlined the API (BC Breaks).
* Refactored code for more readability
* Added adapters. Guzzle as client is now interchangeable.
* Added request and response filters. Users can now modify the Symfony requests and responses to their liking.
I like the idea of moving the adapter into an own package but in the current state of the library it would be exaggerated. Will move the guzzle package into the suggestion and require-dev section.