added automated test units for shape objects

now that this is working properly and now also a key object in the
engine, this will ensure we don't break them in the future :)
[#144] renamed the `getContext2d()` function to `getContext`

actually merged the two previous redundant function into a single one.
And this is now also on pair with the webGL API that only defines a
`getContext` function
updated README to reflect the current supported features
[#370] fixed the background color drawing when the level is smaller than the display canvas
CHANGELOG update

I forget it each time ! :P
updated readme, and added details to setCurrentAnimation
minor casing fix in changelog
removed proxy functions from video.
added details of refactor