v0.2.1 - Upgrade Balance Tweaks

A small update to the Physics Update is now available which should now make the game winnable.
[h2]Change Log[/h2]

• Added game version number to main menu (0.2.x is the Physics Update).
  
• Undocking will now fire retrograde thrusters for just two seconds instead of indefinitely.
  
• Adjusted fuel and thrust upgrades to be roughly linear in terms of how much extra fuel and thrust you get with each upgrade. Cost increase is unchanged.
  
• Adjusted min throttle and ISP upgrades to "max-out" relatively quickly.