improve sequence_builder

[tandav]

• Add access to prefix in sequence_builder constraints
  For example to check that -1, -2, -3 root notes are not equal to current
• clean options type narrowing in SequenceBuilder #66
• more tests
  • test unique and parallel (theres frozenset usage inside)
• feature: take callable which generates options for each step. (now you can only iterate through every possible options)
  pass args to that callable
• upgrade to class
  classmethods for different scenarios: options is iterable, iterable of iterables, callable
• add caching
  • profile cache, is it used in my algo, maybe computing permutations-like sequences didn't use cache (waste of RAM)
  • its kinda not used (ensure this is not because of some stupid bug) sequence_builder.cache_info(): CacheInfo(hits=0, misses=1397182, maxsize=None, currsize=1397182)
  • maybe some parts of the build / constraint checks can be cached
• parallel computing
  • test that parallel results are equal to single threaded
  • paralellize sequence_builder (multiprocessing), make an api to compute on server
  • fix SequenceBuilder(parallel=True) tqdm progressbar #65
• fix sequence_builder(loop=True) not working example #49
• tqdm progressbar
• use iter, next for SequenceBuilder