Excercise msgpack packing/unpacking when using MockServiceContainer

This will enable developer to catch errors that will not have been
possible when we skipped msgpack packing/unpacking, for example
sending a tuple and expecting a tuple in the service, which shouldn't
work since we don't configure msgpack to convert lists to tuples.
Merge pull request #39 from mouadino/exercise-msgpack

Excercise msgpack packing/unpacking when using MockServiceContainer