add support for IE11

IE11 has a pretty different useragent string (Mozilla/5.0 (Windows NT 6.3; WOW64; Trident/7.0; rv:11.0) like Gecko). Because it was so different than prior versions of IE, I introduced a new InternetExplorer11 class to detect it. I dislike this approach, but it seemed cleaner than littering the current IE logic with a bunch of checks to see if it was IE10 or less vs. IE11. If you would like to see IE11 detection in the current InternetExplorer class, I'm happy to redo it. Just let me know what you would prefer.


Thanks!
-Andrew