Search ui tweaks

**Dokku:** https://search-ui-tweaks.dokku.hypothes.is (this is dead for some reason…)
 
This tries to remove the outline around the search box completely to try and reduce the noise. I've left aligned the icon with the content in the stream, I think it looks much cleaner than the current implementation.

![screen shot 2014-08-06 at 18 40 37](https://cloud.githubusercontent.com/assets/47144/3830265/7521772a-1d88-11e4-80ae-9d045d115347.png)
![screen shot 2014-08-06 at 18 40 50](https://cloud.githubusercontent.com/assets/47144/3830266/752235c0-1d88-11e4-8d39-dcdddb4c847c.png)