#2 Allow zooming

[Richard Townsend]

It would be cool if a keyboard modifier could combine with the mouse to allow zooming. Although that might make all other commands difficult to use; some commands might need to be disabled when zoomed in or out.

Some questions to consider:
- Mouse position detection when zoomed in/out
- Game area edge detection
- Resizing... Should it reset the zoom level? Or should it not be applied when zoomed?
- What should be shown when the game is zoomed out? Should the window be resized, or should some of the game area just be dark?