Acceptance tests

Fixes #315.
The current plan which also addresses the problem of allowing the Docker API to be accessed remotely on the tutorial nodes when it is not necessary for the tutorial (https://github.com/ClusterHQ/flocker/pull/897#discussion_r19027788) is to create a new acceptance testing image which inherits the tutorial image. The acceptance testing documentation can warn that all containers on these nodes are not expected to last.