Adds installer script and subsequent readme changes

- Useful for trying to ensure you're running the latest version of each dependency.
- Uses `git fetch` in order not to conflict with working branches, though maybe it should conflict?

![](http://40.media.tumblr.com/5fdbdc7da05f14b6c891c5bb48c5ed52/tumblr_nfixv50U9H1re0c97o1_500.jpg)