Added event listeners to the World
Merge branch 'master' into platformer-example

Conflicts:
	src/world.js
Rendered a simple rectangle to the screen
Created basic player input system. Fixed bug with delta time calculation
Created basic animation system
Created a basic physics system
Created basic collision physics. Only specifically working on x-axis
Improved physics. Still somewhat glitchy
Fixed platformer physics for when one object is moving.
Platformer physics seem to work perfectly for single moving systems.
Fixed issue with colliding from below.
Refactored Physics component into PhysicsBody
Merged in platformer physics and quad tree
Added support for camera systems