add a transparent border around inputs

this prevents the visual jump that happens on initial input focus.

## before
![out](https://f.cloud.github.com/assets/883126/2175415/fcbd999a-95be-11e3-8897-2873105c3cd8.gif)


## after
![out](https://f.cloud.github.com/assets/883126/2175422/0b1d3ee6-95bf-11e3-9a26-d175726bb501.gif)