Use `show` method for all derived types

[wildart]

[codecov-commenter]

Codecov Report

Merging #1363 (b51a977) into master (a350622) will increase coverage by 0.13%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1363      +/-   ##
==========================================
+ Coverage   85.52%   85.66%   +0.13%     
==========================================
  Files         128      128              
  Lines        7863     7863              
==========================================
+ Hits         6725     6736      +11     
+ Misses       1138     1127      -11     

Impacted Files	Coverage Δ
src/mixtures/mixturemodel.jl	74.68% <100.00%> (+4.64%)	:arrow_up:

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