precise the usage of some methods

[artemru]

• to remove :

• cy_safe_slug, cy_is_exceptional, batch_is_exceptional_mask, cy_domain_from_email_lambda

• tools/curve.pyx

• tools/getter.pyx/Unifier

• where - whole module

• karma/core/truncated_relation and cyperf/matrix/routine.pyx/indices_truncation_lookup

• to move :

• indexing/column_index/merge_sort -> tools/sort_tools

• matrix/routine.pyx/merge_sort -> tools/sort_tools

• to document:
  increment_over_numpy_string - A/B testing specific method (add doc and examples)
  rank_dispatch -> document since it's used in LabeledMatrix and there's no external ref

• fast_buddies, vector_distance - extra -dodc

• to see extra usage from KarmaCore :

• KarmaCounter : copy fromkarma/core/utils/counter.py

• fast_sampling_method - to copy karma-core/karma/core/utils/sampling.py

[artemru]

https://github.com/tinyclues/datascience/blob/5f69dd34d3b5903c364581e9839aab78b4bb9921/artem/ab_tests/CdPageviewInc-Copy1.ipynb - A/B tesing usage of increment_over_numpy_string