Support for immutable layouts.
Don't measure temperature, since it's not used.
Add immutable based spring layout.
Do attracts first.
Add benchmark for layouts.
Make more elegant.
Extract the immutable vector to top-level.
Add ImmutableSpringLayout.
Get rid of useless code in ImmutableSpringLayout.
Improve ImmutableSpringLayout.
Change socks plan to return Planner instead of Plan.
Plan takes Planner instead of Plan.
Slight tuning.
Add a parallel variant of the ImmutableSpringLayout.repulse and did some tuning.
Better output in Preview.layout.
Fix step limit.
Smaller max timeout.
Add one more size of socks and output node-count in benchmark,
Seperate parallel and serial immutable spring layout.
Get rid of mass in fixed-mass layouts.