Added the bare bones for the engine.

Will soon start moving code into implementation for testing.
Changed Game class to Engine class

* Renamed game.js to engine.js
* Added comments for engine code

TODO:
* Implement game update cycle
* Implement game draw cycle w/ draw buffer
Deleted game.js?
Blah
Hijacking the beginning of the engine for physics testing.

Hopefully this will give me an idea of how physics will work in the
context of our engine. Also, it will give me a chance to implement a
cleaner setup of the physics environment.

Since this is my first time working with Box2D I expect to have a few such
iterations. This is the beginning of v0.2.
Adding physics interface to handle physics calls.

Define a general interface to handle physics and provide an interface
between the game and the physics engine.

Define functions in the interface to handle conversion from physics units
(meters) to game units (pixel).
Add world setup function.

Add function to setup the world to default settings defined by the
PhysicsInterface object. Function bounds the world by boxes to function
as walls/ground objects.
Add function to draw physics bodies.

Add function to iterate through and draw all physics bodies in the physics
world.

Fix dimension conversion functions in the Physics Interface.
Add box to physics world.

Test physics functionality by adding a box to the physics world.

(Note: Currently, the box loses its position on the first Step() call.
Under investigation.)
Fix physics problems by adding correct timestep.

Add custom implementation of gametimer average for possible use as the
timestep.

Fix timestep passed by engine to constant value determined by target
frame-rate (may need to look into developing a dynamic timestep based on
processing time to account for processing time if processing takes too
long).
Add various static and dynamic shapes.

Enhance testing environment by adding dynamic and static boxes and
circles.
Add planet class to simulation.

Add planet class to facilitate gravity force vector calculations. Proof of
concept for planetary gravity.

(Note: Unmoving objects on planets do not currently go to sleep. Needs to
be fixed.)
Add multiple planets to simulation.

Allow the addition of multiple planets to the simulation.
Testing a simple extra line to see if my paths are set up proper.
Fixed the horrible horrible change that was made entirely on accident.
Added the pony class.
Added friendship.
Oops.
Little bit better.
Fixed the world explosion.