Add Transit Maps

See #33 for previous discussion.

Todo:
- [x] Rename classes to LineSidebarView, MapSidebarView, LineView, SelectedLineView @samhashemi
- [x] Update url routing to /map/:id and /map/:id/line/:id @samhashemi
- [x] General front-end cleanup @samhashemi
- [x] Switch to Google Geocoder @samhashemi
- [x] Add basic actions to MapView @samhashemi
- [ ] Switch to camelCase for JSON api @dget
- [ ] Switch to incrementing ids for Line @dget 
- [x] Make API 404 on non-existent maps @dget
- [x] Add API tests for new endpoints @dget