Refactor object system/moving entities.
    * Added more informative error checking.
    * Removed a bunch of repetitive metatable stuff.
    * Some tweaks to object configuration to allow smoother collision detection.

Refactor collision detection.
    * Hid 'collideRect' and 'collideCirc' behind 'collide'.
    * Change interface to just take two entities.

Formatting.
    * Spaces between arguments on function calls.
    * Spaces between math operators (unless it misrepresents associativity)
    * if statements don't use an outer pair of parens