Feature/grid sizes

Better grid section and styles. Better containers, too.

Of note:
- Breakpoint grid classes should work for *sizes equal to or less than the breakpoint*
- Grids are inline blocks, so there's this bit of annoying extra space. Before, i used negative margin to try and fix, but that got really ugly, really quick. Now, there's a font-size: 0 fix that looks much nicer. Not sure of the ramifications of this, but whatev.
- Looks good in new chrome, new safari, and outdated FF.