Refactor package structure

[zaibacu]

Good ol' setup.py became too unreliable, mostly due to this bug: pypi/warehouse#4079 reported two years ago, but still causing problems. On some computers it works, on some it doesn't. Life is too short for these kind of problems

[codecov]

Codecov Report

Merging #56 into master will not change coverage by %.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #56   +/-   ##
=======================================
  Coverage   91.69%   91.69%           
=======================================
  Files          11       11           
  Lines         614      614           
  Branches      103      103           
=======================================
  Hits          563      563           
  Misses         34       34           
  Partials       17       17           

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