Bookmarklets Section

## Changes
- Adds "Bookmarklets" section above the pattern library's style guide
- Adds a bookmarklet to hide all Drupal admin menus and tabs

![bookmarklets](https://cloud.githubusercontent.com/assets/1479130/2542132/e73aa14a-b5e3-11e3-92ea-55f62a25fbb8.png)

### Notes
This arguably isn't the best place for a collection of bookmarklets as some are application specific. For that reason, this addition should be seen as temporary. We were having trouble adding inline HTML to the production repository's GitHub Wiki page.