Refactor example for easier maintenance

[zmitchell]

There's a lot of redundant code in the various examples to the point that updating winit becomes incredibly painful.

What we need:

• Identify common patterns used throughout the examples
• Extract those common patterns into a utility module/crate
• Rewrite the existing examples to use the crate

[zmitchell]

It would be especially useful to have a function that says if key == "s" so that you don't have to destructure the Key::Character(letter) and check letter = "s" every single time.