Add Miscellaneous API navigation section.

- Adds a Miscellaneous navigation section.
- Moves old top-level Gitignore and Markdown navigation sections into Miscellaneous.
- Moves Meta and Rate Limit navigation sections into Miscellaneous.
- Adds the :new: Emojis section into Miscellaneous.
- Adds alphanumeric ordering to the top-level navigation sections, after pinning Overview and Guides to the top.

All existing URLs remain unchanged. The /v3/misc URL has been added as a summary page for the Miscellaneous navigation section.

![screen shot 2013-09-11 at 23 03 17](https://f.cloud.github.com/assets/65057/1126520/a5d35458-1b25-11e3-9cc4-591bb54f30d6.png)

Hopefully this brings better organization to our API endpoint documentation.

For your consideration. :v: