add benchmarks tutorials and simulation doc strings

[sampan501]

Reference issue

Closes #40

Type of change

Documentation

What does this implement/fix?

Additional information

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[codecov-io]

Codecov Report

Merging #41 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #41   +/-   ##
=======================================
  Coverage   94.97%   94.97%           
=======================================
  Files          18       18           
  Lines         717      717           
=======================================
  Hits          681      681           
  Misses         36       36

Impacted Files	Coverage Δ
mgc/independence/kendall.py	73.68% <ø> (ø)	⬆️
mgc/sims/indep_sim.py	98.33% <ø> (ø)	⬆️

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