Add addons to improve lint checking

[fealho]

Resolve #80.

This is the base PR in which all other addons will be added (each one will be implemented in a different PR).

[codecov-commenter]

Codecov Report

Merging #90 (45fe99d) into master (d2bbd4e) will not change coverage.
The diff coverage is 40.54%.

@@           Coverage Diff           @@
##           master      #90   +/-   ##
=======================================
  Coverage   51.16%   51.16%           
=======================================
  Files          50       50           
  Lines        1503     1503           
=======================================
  Hits          769      769           
  Misses        734      734           

Impacted Files	Coverage Δ
sdmetrics/base.py	77.50% <0.00%> (ø)
...dmetrics/column_pairs/statistical/kl_divergence.py	61.53% <0.00%> (ø)
sdmetrics/multi_table/detection/base.py	83.33% <ø> (ø)
sdmetrics/single_column/statistical/cstest.py	68.42% <ø> (ø)
sdmetrics/single_column/statistical/kstest.py	72.22% <ø> (ø)
sdmetrics/single_table/bayesian_network.py	46.15% <0.00%> (ø)
sdmetrics/single_table/detection/base.py	47.50% <0.00%> (ø)
sdmetrics/single_table/efficacy/__init__.py	100.00% <ø> (ø)
sdmetrics/single_table/efficacy/binary.py	75.00% <ø> (ø)
sdmetrics/single_table/efficacy/mlefficacy.py	0.00% <ø> (ø)
... and 19 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update d2bbd4e...45fe99d. Read the comment docs.

[csala]

Approving this in advance, before all the other stacked PRs are merged into this one, since the rest of changes will have been approved on their own already