Updating pathname to be ie-compatible. Adds leading slash

We've been using this component in one of our projects which I just started cross-browser testing.

IE doesn't add a leading "/" to the pathname all of the time. There's a discussion on [stackoverflow](http://stackoverflow.com/questions/956233/javascript-pathname-ie-quirk), and [backbone seems to do something similar](https://github.com/documentcloud/backbone/blob/master/test/router.js#L29-L31) to add the leading slash.