added basic device orientation handling.
fixed remove event listener call, and corrected the boolean.
created device script, moved device motion logic from input to the device namespace.
renamed properties to match that of the browser API.
Fix `me.sys.scalingInterpolation` when display is resized.
Allow `AXIS.NONE` to be set in `me.game.viewport.follow()`
Add a new private `offset` property to every shape. Only useful for polygons, so far.

- Points for Polygons are always given relative to the first point placed, at position 0,0. The new `offset` is used to normalize the position of the shape.
- Also updated the Platformer example to use the normalized object position instead of the position given by the TMX parser. Again, only useful for Polygons.
Fix typo in Vector2d documentation
This flag does not exist anymore !
Do not share the `ratio` vector among all ImageLayer objects.
moved input event handlers and logic into device namespace. Added super basic example.
[documentation] Mark `duration` argument in me.Tween constructor as optional.
me.Tween: remove unused argument for `start` method.
split up properties, and documented them separately. Added accelerometer to the simple test example
Merge pull request #281 from agmcleod/device-orientation

added a new `me.device` singleton object that will hold device capabilities/information and device specific event management (devicemotion, orientation)
removed the duplicated plugin
moved device.js into a system folder and fixed documentation
Moved all Read-Only device capabilities flag under `me.device`

`me.sys.isMobile` is now `me.device.isMobile` , be careful about this
change in your corresponding html file (if using the melonJS
boilerplate)
updated changelog !
Removed the obsolete 'me'sys.cacheImage' setting as it was not brining any real benefits