URL delimiter captures unexpected things

https://github.com/plainblack/ChiselChat/blob/master/src/js/chiselchat-ui.js#L122

I think the ending there should allow for \s (or the \b isn't working) if you hit shift-enter right after the URL (and maybe right before), and then the URL doesn't work.  Maybe that (\b|$) should be outside of $2?
