Route Reverser

I found reversing a route to be a common task and cumbersome. This pull request would add a switcher that, when clicked, reverses the contents of the "To" and "From" form fields. This feature exists in Google Maps and I copied their strategy, though I made the icon myself.

Note: I attempted to make this change mobile friendly, but am not set up to test it on actual devices.

![screen shot 2014-07-13 at 10 46 45 am](https://cloud.githubusercontent.com/assets/552345/3565323/af957842-0ab5-11e4-893e-f3833d69f100.png)