Add auto bounding box

If there is a property called boundingBox on any layer,
the maxX and maxY of the boundingBox property will be
the width and height of that layer. The minX and minY are 0
allow using bounding box in levels that have w or h smaller than the game w or h - before it was glitchy
Merge pull request #118 from joseadrian/master

Add auto bounding box in Tiled by setting the "boundingBox" property on a layer, with value "true" or 1.
Q.Container.fit() now updates the points.
Q.Container.fit() updates p.w, p.h, p.cx, and p.cy of the sprite.
This was not reflected in the points (as generated using _generatePoints() and _generateCollisionPoints().
fit() now calls these methods to update the points.
Merge pull request #126 from rohitj/rohitj_124_Container_fit_update_points

Q.Container.fit() now updates the points.