Genome visualization

This creates a genome browser to view overlapping reads in a reference region, which can be changed by moving left/right, zooming or typing the specific region. Hovering over a rectangle shows the name of the read. The height of the SVG container with the rectangular reads changes based on the number of tracks. (The variables passed into default.ssp are counterintuitively being parsed from String to Int because they kept getting formatted with commas, even when I tried to replace them...) ![screenshot](https://cloud.githubusercontent.com/assets/4754931/3831402/0faf3264-1d93-11e4-8cca-5c699e0e7c74.png) This is built off of @tdanford's visualization work. Thanks!

Please tell me if you have any suggestions; I only have 3 more days left in this internship and I'd love to get this merged in.