Add search icon asset

:koala: 

Replaces the use of `icon-search` with a local asset so that there is no dependency/request for the Glyphicons asset.

__Before__
![screenshot 2014-08-20 21 29 34](https://cloud.githubusercontent.com/assets/1216974/3980079/5851da6a-285d-11e4-9f30-3e4d4d743a0b.png)

__After__
![screenshot 2014-08-20 21 26 51](https://cloud.githubusercontent.com/assets/1216974/3980061/fdcabfee-285c-11e4-8486-65f35db83f06.png)

/cc @zendesk/quokka 

### Risks
- N/A
`Foo`?