adjust docs example for express 4 bodyParser change

It looks like express version 4 changed such that it's now necessary to explicitly wire up bodyParser components. I added a couple of lines to the example in the README.md docs to help folks out with this. I'm using your fabulous package from vanilla javascript, rather than coffeescript. Apologies in advance if I borked the syntax.

I also put a semi-substantial bit of sample code up in another repo: https://github.com/kwindla/snowshoe-stamp-js-sample

Again, thanks for this package!