Merge feature/box2d-physics into develop.

Most development is currently happening on the [feature/box2d-physics](https://github.com/EbenezerEdelman/inferno/tree/feature/box2d-physics) branch, including non-physics related development (the new event dispatching system, for example), so I think that it should be merged back into [develop](https://github.com/EbenezerEdelman/inferno/tree/develop).