Begin implementation of Discover::Client#register

Signed-off-by: Lewis Marshall <lewis@lmars.net>
Add Dockerfile for running integration tests under Docker

Signed-off-by: Lewis Marshall <lewis@lmars.net>
Add a Rake task to run the integration specs under Docker

Signed-off-by: Lewis Marshall <lewis@lmars.net>
Modify the integration rake task to only bundle if necessary

Signed-off-by: Lewis Marshall <lewis@lmars.net>