Revised: parametrize struct definitions of random matrix ensemble types

[apkille]

Revised version of #96. Parametrizes ensemble type definitions by their Dyson index β, while making some changes proposed in #91.

[codecov]

Codecov Report

Attention: Patch coverage is 61.32075% with 41 lines in your changes missing coverage. Please review.

Project coverage is 46.49%. Comparing base (37f177b) to head (fbdb057).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/HaarMeasure.jl	18.91%	30 Missing ⚠️
src/GaussianEnsembles.jl	80.35%	11 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #97      +/-   ##
==========================================
+ Coverage   42.65%   46.49%   +3.84%     
==========================================
  Files          12       12              
  Lines         830      856      +26     
==========================================
+ Hits          354      398      +44     
+ Misses        476      458      -18     

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[apkille]

@dlfivefifty

[dlfivefifty]

Looks good but can you get the codecov up?

[apkille]

@dlfivefifty should be good to go. I'd like to deal with the remaining missing tests in separate PRs.