[Closes #129] Fixes issue with deepcopy in composite model

[teubert]

prog_server requires copying a model. This functionality is broken for composite model.

Fixed issue by moving more logic into setstate, which is called at construction and deepcopy (unlike init). Also added tests to catch this in the future

[github-actions]

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[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (28dd429) 83.36% compared to head (51ce763) 83.41%.

Files	Patch %	Lines
src/progpy/composite_model.py	96.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #130      +/-   ##
==========================================
+ Coverage   83.36%   83.41%   +0.05%     
==========================================
  Files         100      100              
  Lines       10428    10462      +34     
==========================================
+ Hits         8693     8727      +34     
  Misses       1735     1735              

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[kjjarvis]

Looks good and runs successfully