Change jQuery to $j. Fixes #15

Twitch is adding the `jQuery.fn.popup` method on to the `$j` object
instead of `jQuery` as they use `noConflict()`. Unable to pin down why
this only happened when BetterTTV's chat bar is enabled--perhaps
execution timing, but this change has been tested extensively on all
browsers with and without BetterTTV.
Fix width change for the chat button.