Don't separate media queries from other styles
Use a variable to control breakpoints
Maximum-scale is yucky
Clean up our build of Modernizr

Add tests for media queries and display:table.  Remove unused tests for
border-radius, box-shadow, rgba, transitions.  Also remove flexbox test,
since we'll be moving away from that.
Switch from flexbox to display-table
Add fallback styles for no-display-table

Hasn't been tested yet because we don't currently have a media query
polyfill in place, so IE7 looks mobile.