Add "Launch with Cloudify" to the README

Hi guys, in this PR I'm adding a button that lets anyone **launch a live RethinkDB DB in their browser**.  :smile: 

Under the hood it uses [Cloudify](http://www.cloudifysource.org/) to achieve that. 
I work with Gigaspaces, the company behind Cloudify to get community feedback for the new Cloudify product and we chose RethinkDB as one potential use case. 

This is a proof of concept, not actual production code, so please don't just merge this PR yet. :wink: 
Although just POC, it's fully functional so feel free to play with it and most importantly - send feedback. 
Ideally, if you like it, I'll make it production ready and if not, I'm very much interested in getting your constructive feedback.

Thank you!