Documented Main.elm.
Documented State.elm.
Documented Pod and Planet modules (very similar).
Documented Util.elm
Documented Config.elm
Documented Step.elm
Documented Physics.elm
Switched from using 'p' to denote the pod to 'pod'.

This means it won't be confused with planets.
Added missing paren in a comment.
Documented Render.elm
Merge branch 'master' of https://github.com/WillSewell/orbit-game