title: authenticate_with_http_token evaluates to nil
body: <p>I'm trying to create a very basic authenticator but unfortunately I'm getting nil in return causing my route to 401 since its unauthorized.</p>
  
  <pre><code>[20] pry(#&lt;API::UsersController&gt;)&gt; 
  ActionController::HttpAuthentication::Token::ControllerMethods.authenticate_with_http_token
  NoMethodError: undefined method `authenticate_with_http_token' for     
  ActionController::HttpAuthentication::Token::ControllerMethods:Module
  
  [22] pry(#&lt;API::UsersController&gt;)&gt; cd    
  ActionController::HttpAuthentication::Token::ControllerMethods
  
  [23] pry(#&lt;Module&gt;):1&gt; ls
  ActionController::HttpAuthentication::Token::ControllerMethods#methods:
  authenticate_or_request_with_http_token  authenticate_with_http_token      
  request_http_token_authentication
  locals: _  __  _dir_  _ex_  _file_  _in_  _out_  _pry_
  
  [24] pry(#&lt;Module&gt;):1&gt;
  </code></pre>
  
  <p>Code:</p>
  
  <pre><code>protected
    def authenticate
      authenticate_token || render_unauthorized
    end
  
    def authenticate_token
      binding.pry
      authenticate_with_http_token do |token, options|
        User.find_by(auth_token: token)
      end
    end
  
    def render_unauthorized
      self.headers['WWW-Authenticate'] = 'Token realm="Application"'
      render json: 'Bad credentials', status: 401
    end  
  </code></pre>