Make switching between hit periods work without JavaScript

* Dispense with the drop down, use a tertiary navigation pattern based on bootstraps navbar
* Works without JavaScript
* Makes time period options clearer and is a better indication of which is selected
* On mobile/thin page widths it makes use of the collapsible menu pattern as used in the page header

![screen shot 2014-05-01 at 17 52 16](https://cloud.githubusercontent.com/assets/319055/2854563/7195b9e0-d152-11e3-9c99-a82428a9adfb.png)
![screen shot 2014-05-01 at 17 52 05](https://cloud.githubusercontent.com/assets/319055/2854562/71950414-d152-11e3-86ea-ece7227b6ce5.png)