Implement the Tools Directory

:fork_and_knife: :pizza:

This implements a Tools Directory, a page similar to the Cookbooks Directory. The goals being:

- introduce tools
- highlight recently added ones
- show the various types

Eventually, we should list out descriptions for each type of Tool to give users a better idea of what each one is for and how they are packaged.

Here is what it looks like:

![screen shot 2014-08-21 at 11 17 37 am](https://cloud.githubusercontent.com/assets/928367/3998239/78ba6206-2946-11e4-8b58-8245dcef9ef1.png)

Trello card: https://trello.com/c/UIV6Fp07
You probably want this to go to `tools_path(order: 'created_at')`.