Combining inuit.css and csswizardry-grids

-- Removed a few variables that seemed to be unnecessary with the the new setup
-- Tried to use comments from csswizardry-grids where possible

Don't know if you were planning making a change like this, but my company wanted to use the combined version so I thought I'd see if you wanted to add this. 

The only major change is the removal of the $responsive-extra: it seemed the array allows the user to add breakpoints so I was not sure if this was necessary