Update to reflect changes in nomlib’s API
Fix a few SDL2 issues & bit of time-step clean up

  - Game class:
    * Re-enable toggling full-screen mode
    * Pass the delta_time variable to GameStates::update & remove CPU
sleep "patch"

  - PlayState:
    * Bump the framerate for player2 up to 500ms (was 320ms)
    * Make use of delta_time variable in the player2 animation for card
selection & get rid of the else statement for it