Updated player and entity bounding/hitboxes

x,y coordinates for player and all entities now correspond to upper left
corner of their bounding box. Adjusted all collision, movement, attack,
and teleport code to reflect these changes.
Created player:setBasicAttack() function

Wrote function to set attack variables to those for the basic melee
attack. Function is called before player:melee() on "v" keypress.
Fixed wall collision glitch