Installation instructions don't explicitly state using Terminal

I sent my coworker, Camus, the link for [Installing Python on OSX](http://docs.python-guide.org/en/latest/starting/install/osx/), but it was not obvious to Camus that the instructions for installing `brew`:

    To install Homebrew, simply run
    $ ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

were meant to be run in `Terminal`. I grant that the entire Python Guide might be intended for more experienced developers and that new users could just go to Python.org and download the installer. I would prefer sharing the opinionated guide with a new developer, though, and not have to supplement it with digressions about what the prompt character, `$`, implies, but is not a part of the command that we paste into Terminal.

The link for `install Homebrew` in this guide is somewhat stale, but if you follow it through to the [Homebrew homepage](http://brew.sh/#install), the instructions there are a bit closer to what Camus would need (mentions Terminal, doesn't include the prompt character).
Yeah everything else is fine. I would just rather not explain in painful detail to the reader how to open a terminal application in OSX. I expect anyone reading this guide knows how to use a search engine and can find instructions for that elsewhere. Everything else seems :+1: