* Introduce a request builder.
We inject every dependency (eg RequestFactory and MultipartStreamBuilder) and we do not have to use postMultipart.
* code style
* Use uppercase on http verbs
* Added setters and use getters
* Added tests
* style
* Removed inheritence, Renamed classes, Mark all classes as final
* code style
* Updated docs
* Code style
* Be consistant with the naming of functions
* Fixed tests
* Added base for the new API
* code style
* Added response classes
* Added support for serializer
* The abstract API should not know of Mailgun
* Minor
* minor
* Using a client configrator
* code style
* Put HTTPClient in the configurator
* Do not use the api() function
* Use stable version of Assert
* style
* Fixed tests
* make the httpClient private
* Renamed ResponseSerializer to ResponseDeserializer
* Disabled tests that are testing error messages with Assert
* style fixes
* Refactoring fix
