Fixed bug leading to invalid accessTokens when using Questionmarks in ap...

When you use a '?' in your api-calls the accesstoken gets appended with another '?' https://github.com/Thuzi/facebook-node-sdk/blob/master/fb.js#L268

This leads to a api-call like this one: https://graph.facebook.com/me/friends?limit=10?access_token=vSAEFfionhaWFwai...

You see multible '?' in the request and Facebook can not find the accesstoken anymore because of this