Update forms.css

Removed the gray color of forms' labels. Fix for issue [#89](https://github.com/yui/pure/issues/89)
Update HISTORY.md

Documented fix for issue [#89](https://github.com/yui/pure/issues/89)
Merge branch 'label-color' of git://github.com/AurelioDeRosa/pure into AurelioDeRosa-label-color

Conflicts:
	HISTORY.md