Add cache-busting to static JS and CSS assets

Based on when the app was started, i.e., redeployed.
Address a few issues pointed out by pylint.
Fix failing test--thanks takes an issue argument in the URI
Add /addons/ to root to distribute some browser addons.
Wrong directory >_>
Add Info.plist for Safari auto-update (but I think I missed up).
Set us up to send emails when theres a 500.
Tests to prove that sending emails works
Rejigger URL tests to mirror email tests.

(tweak import path in case you want to run this directly)
Create js/vendor folder for external deps.
Copy the URL into the textarea when the URL is pre-filled.

Closes #120.
Add Ember, Ember Model, Handlebars deps.
Use Ember.prod builds from Grunt, serve debug in dev.
Rename new_index method to index.
Add login/logout from header + avatar.
Pull out feedback/login bar into a topbar.html partial.
Pull out the Browse Issues section into its own partial.
Initial styles for Browse Issues container + key.
Padding tweak for small viewports.
Final tweak to issues key at smaller viewports.