Implement simple date range selector

Let users select a recent date range to filter responses.

**Requires the [date filters PR in localdata-tiles](https://github.com/LocalData/localdata-tiles/pull/120)**. 

Stacks correctly with other filters. 

Currently has 4 date options; A future iteration will have a custom date range selector, but this is a good starting point for many users:
*  All
* Past hour
* Today
* Past 7 days

I'm not entirely happy with the style of the date dropdown -- the native browser widget doesn't match our design. However, I wanted to get this out there, and we don't currently have a dropdown style. 

By default, it says "All responses". Should it say "all dates" for consistency? 

![2014-10-23 05 06 46 pm](https://cloud.githubusercontent.com/assets/86435/4761470/936c8578-5af8-11e4-9464-6397eac84832.png)

![2014-10-23 05 04 55 pm](https://cloud.githubusercontent.com/assets/86435/4761451/5cfc75b6-5af8-11e4-8c71-3d7256f0a56c.png)