Achievements are Ready! — Goppy Steam update #536614

Hello everyone, here's the previously-announced update featuring Steam achievements, which complete the game. Along comes a general difficulty adjustment: taking advice from some testers, I have made everything a bit easier. After all, 'Goppy' is supposed to be relaxing and satisfying, not competitive and frustrating! Finally, some bugs got squashed in the process, like a malfunctioning menu shortcut which nobody noticed anyway. Still.