Adding nginx config to address websocket connection issue.

[rayrod2030]

Based on this stackoverflow post: http://stackoverflow.com/questions/22665809/how-to-configure-ipython-behind-nginx-in-a-subpath this nginx config allows browsers to properly communicate with the ipython noteboook server via websockets.

[rgbkrk]

The Origin header is there for your users' protection, this should be templatized in some way.