Deploy Nbviewer2 ?

This is a request to merge nbviewer2 into master, and deploy it live at the same time. 
Pinging @minrk (sorry, I had to run yesterday) 

We can deploy this one or directly try to carry on with Tornado branch.

Pure Tornado branch have the issue of not beeing tracked by newrelic,
and we probably have to write the caching of data ourself. 

With tornado branch we can use Hosted Graphite it just require to tag explicitely what are the metrics we track.

In any case I have no strong preferencies.