Feature/add initial search layout

~~Open pull request. Please don't merge yet~~
**PR fell too far out of date. Instead copy-and-pasted relevant parts to #188.**

- Adds additional nav item for search
- Adds initial layout for search results page
- Adds yml file with curated search data

Issues:
- Search doesn't actually *work* yet so I'm hesitant about merging this into the live alpha
- The data displayed uses Jekyll to pull from the data yml file, but again, isn't really *searching* anything, so...
- The interactions in the search box need some JavaScript love to be complete (helper text needs to disappear when user clicks in box; search terms need to persist to search results page; etc).

Screenshot
![screenshot 2014-10-15 15 25 13](https://cloud.githubusercontent.com/assets/4827522/4654793/f5d83b1a-54ba-11e4-8350-dd31099bbc72.png)