Added possibility to pass parameters to the authorize path.

[akoenig]

In my current project I need the opportunity to realise a "real twitter logout" which means that it is not enough to erase the session. The user has to login via twitter again if he would like to access the application.

I have seen that there is a "force_login=true" parameter for the "/oauth/authenticate" action in the Twitter API that forces the user to enter their credentials. Unfortunately, I did not find the possibility to add the params to the url, so that I've implemented a "authorizeParams" function in which you can put the params that will be appended to the authenticate url:

            everyauth
                .twitter
                .authorizeParams({force_login: true})

So in my case: If the user tries to login via: '/auth/twitter' he will be redirected to the twitter login page.

I hope that this is useful for someone.

[rishabhmhjn]

Is there any reason not to merge this PR?
It is necessary sometimes to be able to do something like force_login=true while logged in, or supporting multiple twitter logins.