Adding support for sync'ing local hosts.

Adds two commands to the plugin which can be used to manage the hosts file on
the local machine. The current implemention requires that the vagrant boxes
are running. In the future it might be nice to do something smarter with
configuration objects. But this is a good start and solves a lot of pain.

This feature is really important for the SE team. Can we also cut a minor
release for this change once we get it accepted?