use loop to generate prefixed width classes
use mixin for width classes
use mixin for grid push and pull
fix after rebase
refactor mixin further
cleanup files
turn off grid pull
remove extra space
make var overwrittable
make it more DRY
change comment
fix typo and rename settings var
Merge pull request #25 from AlecRaeside/dry-grid

Use mixin to generate classes for widths and grid push/pull