Remove ember.js submodule.

Ember's stable releases are good enough.
Move jQuery and moment.js to vendor directory.

I did not write nor modify these, so they are vendor code.
Also vendor fonts.
Use Font Awesome to shorten the word "downloaded".

(Could find additional use in the future.)

The @font-face hackery in app.css is because font-awesome.min.css
expects to find the font file in a place where it won't find it.  I'll
probably fix that when/if I port the application stylesheets to SCSS or
LESS.