Add interactive demo link to README

[dylanhogg]

I have a deployed a simple AWS hosted web app of this project with its pretrained model at https://address-app.infocruncher.com

It's been up and running for over 6 months and isn't going away any time soon. The code is also on GitHub: https://github.com/dylanhogg/address-app

I thought it could be useful to include a link to it for people to kick the tires and evaluate how well it parses addresses.