Remove Skydock, add minidns stubs

Delete Skydock/SkyDNS/Consul files, as we won’t be using these. Add a
minidns module containing a Dockerfile and a function to build the
image, as well as a MiniDNSContainer that can be instantiated into a
live Docker container with the server.  Add isRunning/start/stop/remove
lifecycle control functions, and add_service/remove_service function
stubs. Port binding still needs to be implemented after we sort out
bridge interfaces. Also add Requests to setup.py requirements, as we’ll
be using it in the function stubs to control minidns.