Viewport event reflects the absolut position and size of a given
container (and propagates them to its children). While the size
event propagates the content size to its children (and sets their
corresponding member values accordingly).
Both events are currently only emitted by `Container`s meaning that they
don't need to be part of the event loop and that they might be removed
later.
Remove examples, add description for design goals in README.md and
apply re-names and naming changes accordingly for the project structure.
Implement a flat hierachry, as the library shall remain pretty simple.
