Added test by matchMedia and fall back to using width

This was a great utility in my latest project, as I had JavaScript features that needed to turn on/off specifically when the browsers were matching a mediaQuery.  I added the following code because not all browsers matched the mediaQuery width and the browser innerWidth (specifically Chrome/Safari).  By testing against matchMedia first, and falling back to the width method it handles things pretty succinctly for all browsers.  I don't think the matchMedia.js code is actually needed, as IE should fall back to just use width if it doesn't exist.

I merged back in the updates, so my previous additions (add a previous breakpoint) no longer is used, but I left in the additional exposed function that lets you query for what the previous breakpoint was (counter to the getBreakpoint function already exposed).