Merge pull request #7 from lnolte/border-box-support

Add Box sizing variable to grid
Revert "Fix incompatible units bug when working with border-box fluid grids"

This reverts commit b198bad29d11ddacdaaa2752a0b8b405612b3196.
Update options documentation to correctly reflect the influence of the border-box setting

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Bump version to 0.4.0

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Merge branch master