soedinglab/prosstt: accepted aye-aye

A busy year and I forgot to make a new release, so now that PROSSTT is published here it is.

major changes:

• new sampling strategies (density sampling, velocity sampling)
• can simulate non-informative genes
• added a lot of example notebooks
• cell size now can vary
• added option for delayed commitment branching ("probabilistic branching")
• PROSSTT can learn hyperparameters from data now

minor changes:

• updated documentation, moved to readthedocs
• now supports newick input and file format (thanks @scottgigante)
• branch naming works better now
• improved how expression programs get sampled, can mostly avoid extreme cases that distort sims