OAuth-based Strategies
Hi @rkusa, thanks for proposing your help.

I'm trying to get koa-passport working with passport-soundcloud.

Here is the code to reproduce my issue : https://gist.github.com/oomathias/273ebe4d7e1ff239590a

The callback is called but nothing happen.
I've tried to place some debug, and it seems stuck at `koa-passport/index.js:69`
`var res = yield auth.bind(auth, this.req, this.res)`

Maybe my code is wrong, i'm new to koa.
