bundle update
Update angular & jquery; serve from CDN in prod

Unminified jQuery and AngularJS are provided for development &
debugging. Production serves from CDNs because it's quicker.
Move navbar to its own AngularJS template

This required making app.js an ERB file. The name of the site (as
defined by config/site.yml) cannot be pulled in a good, DRY way without
making either the AngularJS template or app.js into an ERB template. I
decided to make app.js one because I'd have to add a route in the
Sinatra app just for the AngularJS template. Turning app.js into
app.js.erb required little work.

I could have specified the site's name in an ng-init tag somewhere, but
I'd have to do it twice: once in main_page and once in main_page_mobile.
Escape JS in site name
Add error data for debugging
JS code cleanup & commenting