The EXPECT_EQ should be an assert to prevent a segfault later on.
New Quadtree implementation.

The split and rejoin functions are separate from insertion and removal
respectively.

It gives more flexibility to the Quadtree::setObject function and now
the functions take a fraction of the calculations relating to this
Quadtree.
The ObjectManager::ids function is now implemented with a cache.
TODO of the ObjectManager.

The ObjectManager functions makePaddle, makeBall, and insertObject are
now implemented using ObjectManager::insert!
Added some whitespace to the ObjectManager.h file.