Speedup efsearch more

[matteobachetti]

This uses a bunch of optimizations to speed up by a large factor the Z squared statistics calculation and by a smaller amount the rest of the processing.

[pep8speaks]

Hello @matteobachetti! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file hendrics/efsearch.py:

Line 212:1: E302 expected 2 blank lines, found 1
Line 218:80: E501 line too long (92 > 79 characters)
Line 229:17: E127 continuation line over-indented for visual indent
Line 229:80: E501 line too long (86 > 79 characters)
Line 632:80: E501 line too long (81 > 79 characters)

Comment last updated at 2019-12-20 09:19:46 UTC

[coveralls]

Coverage increased (+0.4%) to 93.487% when pulling aef4ce0 on speedup_efsearch_further into 11a24cd on master.