Adding jaws.QuadTree

Adding quadtree functionality JawsJS.

Using QuadTree.collide(), it will take as arguments two of any objects
that can be inserted into a SpriteList (or even two SpriteLists
themselves) and return if, at any point, they overlap with each other.

If the third argument, callback function, is set, collide will call that
function, with the two objects that collided as arguments, per collision
detected.
Adding width and height to jaws.Parallax

While building one of my demos, I noticed that Parallax was breaking out
of a viewport. This patch, with the addition of a width and height for
Parallax, works toward fixing that problem. (Because it defaults to
jaws.width and jaws.height, all previous code will work properly too.)
Fixed Sprite, Text Testing; Added QuadTree tests

For some reason, jaws.Sprite has lost its "color" option and the
adjusted canvas drawing. This is fixing it again. (It's probably my
fault, but it's still weird it seems to keep changing.)

Re-added text.js (so its tests will now pass) and added quadtree.js so
it can be tested.

Added tests for QuadTree.
quadtrees by dan cox