Queue callback is now a trait instead of a function
Merge branch 'master' into manu-queue-callback
Cleanup leftovers
Merge branch 'master' into manu-queue-callback

Conflicts:
	bwl-core/src/test/scala/com/wajam/bwl/queue/log/TestLogQueueFeeder.scala
	bwl-core/src/test/scala/com/wajam/bwl/queue/memory/TestMemoryQueue.scala
Merge pull request #33 from wajam/manu-queue-callback

Queue callback is now a trait instead of a function