2.0.0: Merge branch '1.8' into 2.0

Don't forget to read the UPGRADE file !

This new major version is ready after months of beta !
It contains many features (some of them are BC and are included in 1.8) such as:

• a more powerful version listener
• support of the symfony serializer (and serializer abstraction)
• new http verbs annotations
• a trait for controllers
• removal of the ExceptionWrapper in favor of the serializers normalizers

Don't hesitate to ping us here or on twitter if you have any feedback :)