Intial Batch storage
Change push to assign to better clarify intent
stamps implemented for envelopes + tests
Add support for Batch in producer
test hhvm on travis
cleanup array_merge and scalar check
Move Batch and Message around in Producer in order to have a more correct exception message if it is given a weird value
Middlewares
add batch stamp to envelope in Batch
add testcase for envelope stamp when created in batch
dont install redis on hhvm
Make properties private as the class is final
Abuse the Message interface by letting Batch implement it. Return to the original produce typehint
Introduce a new Status ValueObject
Add description to storage
Add test for register
Convert into Subscriber