Updated to version 1.8.12-beta: 4 bug fixes

Version 1.8.12-beta fixes a few things:

• Issue 250 - Stabilise racer at high speed
  • fixed 
  Issue 248 - Turn nighttime brightness up a bit
  • much better now. Easier to see terrain at night
• Issue 246 - Fix clipping stuck through walls
  • improved, but needs more work
• Issue 242 - Music not working on Windows .exe build
  • fixed