Only search once when search term changes

I get super excited when searching for emoji and notice that keystrokes are dropped quite a bit for me when I type fast:

![before](https://cloud.githubusercontent.com/assets/65323/3212083/875e580e-ef43-11e3-8245-87778a2585d6.gif)

I think part of the problem is that we are searching twice every time the search term changes: once in the keyup callback and once when the location hash changes. This pr removes the extra search calls and I'm no longer able to drop keystrokes by typing fast:

![after](https://cloud.githubusercontent.com/assets/65323/3212084/8b08a748-ef43-11e3-9608-ae7ae3fcbae3.gif)