Ekdist -- exponentiated Kumaraswamy

[JJNewkirk]

• [Wikipedia](https://en.wikipedia.org/wiki/Kumaraswamy_distribution
• The exponentiated Kumaraswamy Distribution and its log-transform: Lemonte et al https://www.jstor.org/stable/43601233
  I believe my functions are accurate; however in testing the mean of the current kumaraswamy.jl the did not match in some cases. I believe this to be an error in the kumaraswamy.jl in the version I was using. The EK distribution has the Kumaraswamy as a special case, so it is easy to test keeping gamma = 1.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 74 lines in your changes missing coverage. Please review.
✅ Project coverage is 85.64%. Comparing base (e5d4fef) to head (327596c).
⚠️ Report is 14 commits behind head on master.

Files with missing lines	Patch %	Lines
src/univariate/continuous/ekdist.jl	0.00%	74 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1951      +/-   ##
==========================================
- Coverage   86.36%   85.64%   -0.72%     
==========================================
  Files         146      147       +1     
  Lines        8788     8863      +75     
==========================================
+ Hits         7590     7591       +1     
- Misses       1198     1272      +74     

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[ararslan]

Some preliminary suggestions and comments, haven't reviewed everything at the moment.

[JJNewkirk]

All the suggestions were helpful and reasonable. Comitted as suggested.