Link to new oauth2 based raven

A google search on "Raven django cambridge" bought me to an old github repo which links here. I knew I wanted to use the newer oauth2 based Raven so had to search again. I thought it might be useful giving a pointer to people who know what they are doing and a steer to people who don't realise there is a newer protocol.

I'm not sure "deprecation" is the right word - I realise these things can get political, but I couldn't off the top of my head think of a better title!