bugfix issue #159 : Do not merge TRBL values having \9 (hack for IE8)

Hi,

I make a quick bugfix for issue #159, by disabling merging when a trbl (padding/margin) property had a values with a `\9`. 

I don't know if it make sense to develop more and handle the `\9` case like the `!important` statement, and merge all values with a '\9' : Like `padding-top:1px\9;padding-right:1px;padding-bottom:1px;padding-left:1px\9;` => `padding:1px\9 ` ?