Issue #12 Work - IsKeyPressed / Nappis Cleanup

Started working on updating the code to use more of the SDL2 KeyState
mechanics. One of the things that I've learned is that to determine
whether or not a key has been pressed, the state variable already has
that laid out for me. This means that the Nappis struct is almost
unnecessary.
Issue #12 Fix - KMOD don't work

As the title states, I discovered that by changing to KMOD_CTRL / _GUI /
_ALT, the code wasn't working.