declare mqChange (and a couple other variables)

declaring a few variables to fix an issue with registering multiple callbacks to the same media query in fallback mode. Basically, the resize handler was always calling the `mqChange` function as created by the last caller to `mediaCheck`.  This was okay for the most part as it receives `mq` and `options` arguments, but it uses the `breakpoints` object via the closure to track the current status of the breakpoint.  This meant that only the first handler registered for a specific query would get called when entering/exiting.