A way to not count impressions on responsive hiding of ad blocks

I had the need to not display certain ads when browser dropped below a certain width. I could hide the blocks with the css of "display: none;" but then the impression was still being counted. So I updated the simpleads.cycle.js to check to see if the containing block had a display attribute value of 'none', and if so, then not call the impression callback. I'm posting a patch here in case this is useful to anyone - it may be a bit specific in nature for general use, but I'm happy to refactor if anyone has the need.