title: Variable in Player State in Lua not updating as expected
body: <p>In the following code, the value of self.player.x is assigned to self.x is assigned at init and tweaked a little bit to the left or right when the state is entered.  The PlayerPilotState then manipulates self.player.x every frame and my expectation is that self.x would update along with it.  Items such as the tilemap, which are assigned to player as def.tilemap when the player is instantiated, do update as the map changes.  How do I ensure that variables such as self.x will update themselves as well?  I know that I can update that variable under update every frame, but it seems ineloquent and since I'm fairly new to coding, I don't understand why the player.tilemap does update whereas this variable doesn't.  Thank you!</p>
  <pre><code>function PlayerPilotState:init(pilot, passenger)
      self.player = pilot
      self.passenger = passenger
      self.animation = Animation {
          frames = {2, 3, 2, 8},
          interval = 0.1
      }
      self.player.currentAnimation = self.animation
      
      -- x value at middle of players to make collisions more readable
      -- and scalable (for left/right pilot/passenger cases)
      self.x = self.player.x
  end
  
  function PlayerPilotState:enter(params)
      -- determine which side passenger is riding on 
      self.ridingSide = params.ridingSide
      if self.ridingSide == 'left' then
          self.x = self.player.x - 1/2 * self.player.width
      else
          self.x = self.player.x + 1/2 * self.player.width
      end
  end
  </code></pre>