Possible solution for issue 108

Thanks for the awesome library of mixins!

I've found a simple solution to issue 108, i've added an extra **lesshat-selector** to the end of the text that is returned from keyframe js.

I'm not sure if this is the best way to do this, but it's a stop gap for the time being.

NOTE, i used slice OVER replace because it may be possible to match that pattern elsewhere. Where as slice will always remove exactly the last thing that was added to the end of the string.