Import code from badgr.co

This addresses #37. I approached this by moving the existing static PNG and SVG files into a `static/` directory. I added https://github.com/cainus/shielded as a submodule and brought over the Aspen + Redis implementation I came up for the web service. This is deployed at:

http://origin-shields-io.herokuapp.com/

@olivierlacan We can CNAME `origin.shields.io` to that. Once I have the CDN in place I'll get you the DNS entries for `shields.io` itself.

This pull request is ready for review.