update grid-units to have IE-specific widths, and use new grid classnames
prettify spaces and braces
Remove CSSLint ignore + s/default-*/pure-d-*

The .default-* classnames should be prefixed with .pure-
However, .pure-default-x-y seems too verbose, so I changed
it to .pure-d-x-y.
Change default classnames back to .pure-u-*

After thinking about it, it makes sense to just keep
these as .pure-u-* to preserve back-compat and so that
people don't get confused with the fact that these units
are the "default" units.
add back common rules for all grid units
bump up decimal places to 4 units, remove *width for `pure-u-1`
update HISTORY.md with fix for #154
Merge branch 'grids-ie7-fix'

Conflicts:
	HISTORY.md