login in controller not actually called
version: 1.3.0

When login a user in controller, I found the function not really called. the login function return a bound Function:
https://github.com/rkusa/koa-passport/blob/master/lib/framework/koa.js#L46-L48

I am supposed it should actually call the delegate login:

> ```
> ctx.login = ctx.logIn = function(user, options) {
>   return login.bind(req)(user, options)
> }
> ```
