A  a button to the readme: Launch with Cloudify

Hi there, in this PR I'm adding a button that lets anyone launch a new instance of the demo Play app in their browser.  :smile:

Under the hood it uses Cloudify to achieve that. 
I work with Gigaspaces, the company behind Cloudify to get community feedback for the new Cloudify product and we chose Play 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 functional (and simple at the moment) 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!