Expanded the README a bit.
Combined the yum module invocations into one.

Apparently you can't have multiple of these in the same task; some of the
packages weren't being installed.
Moved the installation of dev tools into its own task.

Right now, this is just git.
Added vconfig and bridge-utils to the HaaS's deps.
Added python-virtualenv to the dev tools.

From here, the rest of the python packages can be installed by the developer, in
their own virtual environment.

The package is in EPEL, not the main CentOS repos. We probably should be either
finding a way to make sure the repo is enabled, or just assume it is, and
install from there, but for now we're doing this.
Added gcc to the dev tools.

This is needed for building python c extensions.