Declare a width value regardless of direction in isolation mode.

Currently a width value is only printed when $direction is set to 'ltr' or 'both'  in isolation mode.  Setting $direction to 'rtl' sets margins but no width.  Which breaks the grid for rtl only sites.

Here is a gist with test Scss. https://gist.github.com/pixelwhip/6970064  I'm getting a 500 error trying to save it with sassmeister.