Wording update, new resource content

Now that Outlines have been fully deprecated, home page wording needed changing to match context of "Workbooks".

Added download resource to Cheat Sheet PDF and GitHub Guides per https://github.com/github/training-materials/issues/31.

![screen shot 2014-02-25 at 2 02 53 pm](https://f.cloud.github.com/assets/352082/2262996/4d1b31a0-9e60-11e3-9295-27d1efcee450.png)
![screen shot 2014-02-25 at 2 03 01 pm](https://f.cloud.github.com/assets/352082/2262997/4f03c978-9e60-11e3-8f2e-ca7da87509e2.png)