Removed animation for now.
Root now loads sign up.
Enabling button when valid on sign in and sign up.
Moved stage style onto child div for a better empty state.
Removed unused footer tag.
Really basic error styling.
Added a temporary spinner to account creation.
Lots of UI clean up.

This gets us closer to the mocks. Still not 100%.
Merge remote-tracking branch 'origin/master' into ui-smoothness

Conflicts:
	app/scripts/templates/sign_in.mustache
	app/scripts/views/base.js
	app/scripts/views/complete_sign_up.js
Updated password reset views.
Cleaned up settings and age verification failure page.
Fixed issue with images in dist.

- Moved images into CSS as background images.
- Now delivering different images for retina.
Added change event for inputs to enable form.
Reworked empty stage handling.
Replaced animated GIF spinner with CSS animated PNG.
Fixed responsive stage.
Merge pull request #236 from mozilla/ui-smoothness

UI Improvements