Create the LESS structure of the v3, responsive grid.
Ignore the outputted CSS file from the new grid.
Add v3 Grid to compression script.
Move grid variables to individual file
Add generic clear-fix rule. DRY
Add separate styles for IE8 overrides

* IE8 doesn't support `rem` measurements
* IE8 doesn't support media queries
Remove tracking of CSS output for IE variation file
Add rule for cascade
Merge pull request #416 from smeranda/grid-v3

Implementation of Grid v3