Design overhaul

This is a moderate design overhaul, going with a dark theme with mild blue hints. Changes include:
- Created a logo and favicon(currently just going with 'NOLA Crime Heatmap' as the logo text, might easter-egg it later)
- The map canvas is now viewport-flexible: there should basically never be a scrollbar for the page and the map will extend as low as the viewport's bottom edge. This *does* have the side-effect of cropping off the gmaps copyright and such info, but meh.
- The copied-over NOLApartments-specific styling has been purged.

A separate note:
- There's an argument to made that some SRE could be preserved by moving the logo into where the fieldset currently is or at least reducing the gutter sizes, but I'm going with this approach at least for now.

The future:
- I'd like to do a responsive implementation for the filters, maybe having a hidden select element become visible at a certain width breakpoint.
- Might tweak the logo to have a shadow or outline or something

![screen shot 2013-08-15 at 12 01 40 pm](https://f.cloud.github.com/assets/2473115/970056/7606b7e4-05cf-11e3-9477-907533059958.png)