Added one more are test
Listening to graph changes
Changed variable name to body, to avoid confusion
Added 'step()' check for layout rectangle
Added node pinning
Make sure we covering all bad input
Exposed isNodePinned, added more pinnign tests
Verifying original position is preserved
Note to future self - extract it to a separate place
Added node/links removal tests
Just to make sure we cover merge() as well
Can dispose layouter
No need to track coverage