Linux fixes

[gradientvera]

oh god kivy is a mess, oh fuck python is worse than I remember

Here's a list of changes

• command_shortcuts has been changed to command-shortcuts. Apparently the underscore caused an assert error on linux. Huh!
• takethat.wav isn't a thing but takethat.mp3 is so I changed it.
• apparently on linux, you need to rewind all sounds back to 0. That's fun! So I added a [...].seek(0) line everywhere I could.
• load_wav on textbox.py now uses SoundLoader in platforms that aren't windows.

By the way! Funny stuff! You need to run this command: # pip install https://github.com/matham/ffpyplayer/archive/master.zip For audio to even work on Linux. If audio doesn't work, MO refuses to join the server for some reason! So yeah. Might want to add that somewhere in the wiki/install guide.

Before merging this PR, please test that this works on Windows without issues. I have only tested this on Linux.

[Weeping-Cat]

The world is now a better place.