Social Auth

**NOT YET READY FOR MERGE**

A few questions from starting work on this @benjie ...

1. How do you wish to do database migrations, I need to add a`twitterId`, `facebookId` and `githubId` into the user table. Although this is a trivial migration is it worth setting up Sequelize migrations now?

2. I've used `passport` as everyauth kinda blows nowadays due to lack of continued service support and other issues. Passport handles it's authentication by mounting a users profile to `req.user` for each request. Looking around quite a lot will be updated to use that structure. Are you ok with this or would you prefer modding passportjs to use your custom authentication/session handling?

3. Do you use JSLint or equivalent, if so you might want to publish the preferences for the project ;)