@IBAction func facebookLoginTapped(sender: AnyObject) {
 
    //
    let ref = Firebase(url: "https://XXXX.firebaseio.com")
    let facebookLogin = FBSDKLoginManager()
    facebookLogin.logInWithReadPermissions(["email"],fromViewController: self,handler: { (facebookResult,facebookError) -> Void in
        if facebookError != nil {
            print("Facebook login Failed. Error \(facebookError)")
        } else if facebookResult.isCancelled {
            print("Facebook login was cancelled.")
        } else {
            //successfully logged in
            //get facbook access token
            let accessToken = FBSDKAccessToken.currentAccessToken().tokenString
            //use access token to authenticate with firebase
            ref.authWithOAuthProvider("facebook",token: accessToken,withCompletionBlock: { error,authData in
                    if error != nil {
                        print("Login Failed. \(error)")
                    } else {
                        //authData contains
                        print("Logged in! \(authData)")
 
                        //pop loginvc back to uservc - DO I NEED TO GET MAIN THREAD HERE BEFORE DISMISSING VIEW CONTROLLER
                        self.dismissViewControllerAnimated(true,completion: nil)
                    }
            })
        }
    })
}