Implement simple physics class

[thomas-alrek]

GameObject should have a Physics prototype, that implements a crude physics engine. This engine should also take into consideration each GameObjects rotation, if possible, and implement methods such as addForce().

We might consider addign support for friction too.

[thomas-alrek]

Use this as a reference http://gamedevelopment.tutsplus.com/tutorials/how-to-create-a-custom-2d-physics-engine-the-basics-and-impulse-resolution--gamedev-6331