Fix whitespace collapse; add modifiers
Fix whitespace collapse; add modifiers

* Change `Grid--center` to `Grid--alignCenter`.
* Create `Grid--alignRight`.
* Use `font-size:0` to collapse inter-cell whitespace (no IE 8 support).

The new method for collapsing whitespace relies on `rem` support to
reset the font size in cells. IE 8 does not support `rem` units. If IE 8
support is needed, a preprocessor can be used to generate `px` value
fallbacks.

suitcss/suit,suitcss/suit