Options Menu Added (Volume, Key Bindings)

I've added an options menu to the project, accessible from the main menu. Not as difficult a task as I thought it could be; I probably could've added both volume sliders and rebindable controls much earlier if I had thought to look into it. Now I've got one less excuse to procrastinate on starting work on the "Game 4"s of the 20 Games Challenge.

I might add an options button to the individual games' pause menu, or I might not. We'll see.