New deploy:minimal task

This task only pull in new code, restarts the server and warms it.

Unlike the other tasks, no clearing of caches is performed.
Use NET::SSH::Shell for deployment

This creates a "real" login shell that has the correct
environment for running commands that require chruby.

It also multi-threads the connections for parallel multi-host deploys
Do not run jammit as www-data user.

The sudo was needed in the past so the assets directory
ownership would be correct, but isn't an issue now.