Add and refactor tests for decomposition component

[moCello]

Also add a simple example as to how the scalar will be decomposed.

Resolves #738, resolves #704

[codecov]

Codecov Report

Merging #750 (03aa036) into master (8575e27) will increase coverage by 0.10%.
The diff coverage is 93.75%.

❗ Current head 03aa036 differs from pull request most recent head 38aaa09. Consider uploading reports for the commit 38aaa09 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #750      +/-   ##
==========================================
+ Coverage   85.23%   85.33%   +0.10%     
==========================================
  Files          54       54              
  Lines        4145     4167      +22     
==========================================
+ Hits         3533     3556      +23     
+ Misses        612      611       -1     

Impacted Files	Coverage Δ
tests/decomposition.rs	88.46% <93.18%> (+11.79%)	⬆️
src/composer.rs	91.05% <100.00%> (ø)

... and 1 file with indirect coverage changes

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[ureeves]

LGTM!