Update tutorial03
Update tutorial03

* This updates tutorial03 to do some more interesting things, like run
  the entire program as a function (to try and clean up memory from
  hge.New()). This also shows an alternative approach to using global
  functions for the render/frame functions (and using closures within
  them.)

losinggeneration/hge-go,losinggeneration/hge-go,losinggeneration/hge,losinggeneration/hge