Minor UI improvements and a bugfix

* Updated the highlight style of matched substrings to fit that of Xcode's "Open Quickly" dialog.
* Select first entry automatically to save a keystroke
* Fixed crash when selecting a non-match

I hope the new styles look good on Yosemite, which I noticed you are running.

![screen shot 2014-08-16 at 11 42 19 pm](https://cloud.githubusercontent.com/assets/1256911/3943938/1f0901e6-25da-11e4-89b2-3fb3d1120292.png)