fix(auth0): fix access and id token assignments

Current Auth0 plugin assigns the Auth0 id_token to the access_token
object. This fixes that and now you get the Auth0 access_token &
id_token correctly assigned.

This is breaking change, see issue #397

src/authLock.js

@@ -74,7 +74,8 @@ export class AuthLock {
           this.lock.hide();
         }
         resolve({
-          access_token: authResponse.idToken
+          access_token: authResponse.accessToken,
+          id_token    : authResponse.idToken
         });
       });
       this.lock.on('unrecoverable_error', err => {