feat($repos): display selected clickable repo name #3

- All dependencies are now pulled from a CDN, except ember.js
- Remove modernizr.js (not needed anymore)
- Repos route will simply display the repo_chooser modal
- Current selected repo is present in the center of the header
- Current selected repo is clickable to expose repo chooser modal

TODO:
- Better caching (see TODO in Nimble.Cache module
- Split some logic in RepoChooserController into an Object/Model?