Adding a new Canvace.Timing module which provides abstraction of the timing APIs provided by the browser.

It currently provides a static Canvace.Timing.now() method, which wraps around window.performance.now() where available, or Date.now() otherwise.
BROKEN - The prototype of the TileMap.rectangleCollision method has changed.
STILL BROKEN. Changing argument order.
Fixing a bug which occurred with the latest version of Firefox.
Some browsers don't have window.performance at all.
Code style.
Lint.
Browser API may use this.
Sketching the docs for Canvace.Timing.
Lint.
~
Adding previousPosition field to internal instance objects.
Merge branch '130115-timing' into 130115-physics
Bugfix in Canvace.Timing.
Merge branch '130115-timing' into 130115-physics
Removing Canvace.Timing.animationStartTime().

It's better to use Canvace.Timing.now() to measure times, also inside of the requestAnimationFrame() callbacks, since the timestamp passed to the requestAnimationFrame() callback has a higher resolution on some browsers (e.g., latest Chrome uses microseconds instead of milliseconds).
~ Canvace.Timing.
Merge branch '130117-timing' into 130115-physics

Conflicts:
	src/RenderLoop.js
	src/Timing.js
Adding previousPosition.
~ DebugEffect.