Document how to create custom views (pages)

Hey!  I was just helping someone build a custom page in their app and I realized that we don't really have any documentation around this.  If you're new to Express this is really valuable information to include.

Here is my attempt, ping @rdegges to review.

P.S. here is the SO question that I was answering: 

http://stackoverflow.com/questions/26022351/stormpath-user-information/26042602