Move HashGeneration to dedicated Class

In order to use HashGeneration in Notification process, I moved it to a reusable class.

More over, in order to improve quality :
* I replace curl process by Guzzle
* Reduce Public Code API for Client
* Improve tests Client
* cleaning
Add dedicated class to read status from Be2Bill
Rename 3ds callback stuff to generic callback

Behavior will be the same for notification
Be2BillRequest validate hash before creating itself
update tests
Remove dependency to SymfonyRequest
Simplification and separation domain <=> infra
Add cert for SSL
Merge pull request #26 from tyx/feature/notification

Introduce possibility to handle all kind of callback