Starts working out the Quadtree class
Makes cnavas_dla match 720p resolution
Adds input validation to Quadtree
Change Quadtree#contains? to Quadtree#cover to more closely match the ruby standard library
Adds Quadtree#contains?
Change Quadtree#cover? to Quadtree#covers? because it reads better
Adds Quadtree#within
Adds first test for quadtree searching
Actually implements quadtree subdivision