cssFloat is only accessible as styleFloat on IE8

#1841
This now does the same thing as line 100, increasing the surface area if we need to change how we remove styles. Can we consolidate? We could probably just reassign `styleName if === 'float'`, then leave this whole if/else block alone. The part about checking expansion isn't great since it hits different values (though `float` won't be expanded so that's fine).