Release v1.18.0 (for Beat Saber v1.17.0, v1.18.0)

See the README file for installation and usage instructions.

Adds:

• beatmap.color representing the colors used by the environment. See protocol.md for more information. (Closes #27)

Fixes:

• Playing multiplayer causes future maps played in singleplayer to not fire events correctly. (#74)
• Tutorial should no longer cause exceptions to be logged. (#74, by @Shadnix-was-taken)
• levelFailed callback not unregistered correctly from the gameplay manager.