Use more robust way of removing whitespace.

As per this Tweet by @thierryk:
https://twitter.com/thierrykoblentz/status/305152267374428160

A change introduced in Chrome 25 breaks the previously used method of
removing whitespace. This update to csswizardry-grids uses a far more
robust method, but this commit can be picked back out if the Chrome dev
team revert their changes.