update(ripple): renames 'md-active' to 'md-highlight' for ripples

Renmae ripple `md-active` since it conflicted with tabs attribute.

Close #727.
refactor(style): this restyles parts of the site's layout

enhance(style): added angular logo and switched to red theme

enhance(style): updated toolbar colors for red theme

enhance(ripple): adds a minimal timeout to make sure that updates are complete before creating ripple

feat(theming): adds md-theme-levels directive

enhance(nav): sets focus state for nav items