Add physics and convenience dependencies.

- lodash
- when
- box2dweb
- boxbox
Set body margin to 0.
Add Actor, Level, and getWorld().

Actor is the base type for objects in a level.

A level defines, through json, and supports assets to load and actors
to contain in a level of the game.

getWorld provides a little convenience around creating a boxbox and
getting a named box.
Add PlayerActor, player actor and level0 data, and create that level.
Add a working-background-color. 30% of the color "sky".
Merge pull request #1 from mzgoddard/graphics-init

Graphics init!