Express now removes all trailing slashes.

I didn't like how some URLs with a trailing `/` just ended up somewhere else entirely. At first I wanted to change the Backbone router, but apparently this wouldn't be the correct approach since multiple differing URLs would identify the same page (I lost the SO thread).

It's now done through Express middleware, as described [here](http://stackoverflow.com/questions/13442377/redirect-all-trailing-slashes-gloablly-in-express).