Specify that you need to install homebrew and run brew update
Use normal console style
Move the virtualenv install stage to the docs
Revert "Move the virtualenv install stage to the docs"

This reverts commit a8d8d6ad224a325c26f6175dd124a3cdd50e70c7.
Merge pull request #474 from ClusterHQ/require-homebrew-452

Specify that you need to install homebrew and run brew update.

Fixes #452.