Get Postgres working
Use salt's ssh_known_hosts state
Create database in salt, other cleanup
Don't need to install pip and virtualenv from fabfile because salt already did
Get Vagrant working better

Main change in this commit is to add the `vagrant` user to the `admin` group so that
it can sudo without a password. Vagrant expects that to work and various vagrant
commands fail otherwise.

Also, set ALLOWED_HOSTS in the staging config to wildcard since our nginx config
checks the host already and it was 500'ing.

Also, quiet down some of the operations in the fabfile like `pip install` and
`git clone`.

Also, more comments.
A few more doc updates
Merge branch 'getting_postgres_working'