Change tree fall sound to mono to solve sound positioning

[Dariensg]

Fixes #38

Minecraft's sound positioning system does not work with stereo files unfortunately. I went ahead and used a sound converter shell script I had handy to convert your audio file to mono, fixing this issue. I've tested before this modification and after, and it does in fact resolve the sound positioning issue!

[ThePandaOliver]

Thanks so much, i know nothing about minecraft's sound system at the moment so its nice get some help with this.