Add the implementation of Expected Error Reduction active learning algorithm

[codecov-io]

Codecov Report

Merging #93 into master will decrease coverage by -1.68%. The diff coverage is 21.21%.

@@            Coverage Diff             @@
##           master      #93      +/-   ##
==========================================
- Coverage    77.7%   76.03%   -1.68%     
==========================================
  Files          31       32       +1     
  Lines        1081     1114      +33     
==========================================
+ Hits          840      847       +7     
- Misses        241      267      +26

Impacted Files	Coverage Δ
...ibact/query_strategies/expected_error_reduction.py	21.21% <21.21%> (ø)

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[yangarbiter]

Please write tests.

You can take quire's test as example since this is a slow algorithm.