README.md: git clone url, "folder" -> "directory"
fixed `package.json`: added `coffee-script` dep.
`core/Node.coffee`: getters and setters

The properties `parent`, `position` and `rotation` now have to be
changed via setters.
Getter example: `node.parent()`
Setter example: `node.position new Vector 1,2`
minor tweaks: DRY, better comments
`core/Block.coffee`: added `_update` method
`core/Canvas.coffee`: tweaked comments
added `core/Matrix3.coffee`

`Matrix3` will be used to apply all position and rotation
transformations from the root down down to a node. This make absolute
drawing onto the canvas possible.
`core/Node.coffee`: added `_update` method

Whenever the user changes a node’s parent, (relative) position or
(relative) rotation, the `@_absolute` transformation matrix gets
recomputed.
added absolute drawing

The shapes will now absolutely be drawn onto the canvas.
tweaked comments: added `todo`s
`README.md`: changed default dist size to 12kb

Due to the absolute drawing mechanism (incorporating an additional
class), the library size went up to about 11k.

The library size will be shrinked down further later.
rebuild `/dist` files