Typography Updates v1

Take a look and let me know what you think. `test.stpwrk` has all the styles in it for easy viewing.

A few notes:
* changed `ems` to `rems` to avoid cascading issues. They are [supported in everything but Opera Mini and IE8,](http://caniuse.com/#feat=rem) so that seemed reasonable
* bumped up the `h1` size for a *pow* option
* `code` displays weird but that’s the newline issue and the patch you are working on should cover it
* added an accent color on h6; it can obviously be customized — I just like coral
* changed black to a cool gray — this should not be customized because gray is better than black
* added `box-sizing: border-box` to have the padding & margin work as expected and not overrun the table