fixed https chat linking

This is a fix for the issue listed here, http://code.google.com/p/bigbluebutton/issues/detail?id=1566&can=1&sort=-modified&colspec=ID%20Type%20Status%20Priority%20Milestone%20Owner%20Component%20Summary%20Modified

Previously if you entered https://www.google.com into the chat it would find the "www" first and then attach "http://" on the front of the linked address making an invalid URL