Acceptance tests

Fixes #315.
Well I meant that name of the application might be unique to the test run, perhaps a common prefix with a `random_name()` suffix.

Having run the test suite, I'd quite like to be able to run `docker -H tcp://172.16.255.252:2375 ps  -a` and see  that the mongo application *had* been running on node1....although I don't actually remember whether flocker now deletes non-running flocker containers from nodes.

And perhaps I'm only interested in this information in the event of a failure...in which case cleaning out all containers before each test wipes out the evidence of previous failures.