Cloud Networking

PR for Rackspace networking. Unfortunately, it looks like none of the Rackspace operations for this service can be delegated to the Openstack Neutron code due to differences in URLs and `Network` objects.

- [x] Networks
 - [X] Operations
 - [X] Unit Tests
 - [x] Acceptance Tests
- [x] Virtual Interfaces
 - [X] Operations
 - [X] Unit Tests
 - [x] Acceptance Tests 
Yes, I'd meant to use `testing.Skip()` if there weren't any running instances, but moving this service to `compute` will make it easy to use the testing functions @smashwilson wrote for launching servers.