Future<Null> signUp() async {
    prefs = await SharedPreferences.getInstance();

    this.setState(() {
      isLoading = true;
    });
    FirebaseUser firebaseUser = await FirebaseAuth.instance.signInWithEmailAndPassword(
      email: _emailController.text,
      password: _passwordController.text,
    );
    ScopedModel.of<User>(context).changeId(firebaseUser.uid);
    ScopedModel.of<User>(context).changeName(firebaseUser.displayName);
  }