Uniform endpoints

[alanlujan91]

Addresses: #1178

Please ensure your pull request adheres to the following guidelines:

• Tests for new functionality/models or Tests to reproduce the bug-fix in code.
• Updated documentation of features that add new functionality.
• Update CHANGELOG.md with major/minor changes.

[codecov-commenter]

Codecov Report

Base: 72.79% // Head: 72.81% // Increases project coverage by +0.01% 🎉

Coverage data is based on head (4e56ac4) compared to base (1539850).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1180      +/-   ##
==========================================
+ Coverage   72.79%   72.81%   +0.01%     
==========================================
  Files          72       72              
  Lines       11793    11800       +7     
==========================================
+ Hits         8585     8592       +7     
  Misses       3208     3208              

Impacted Files	Coverage Δ
HARK/distribution.py	82.57% <100.00%> (+0.10%)	⬆️
HARK/tests/test_distribution.py	100.00% <100.00%> (ø)

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[sbenthall]

Merge conflict and CHANGELOG update please

[sbenthall]

Are these points equiprobable with the endpoints included, and if not, how can the pmv be accurately formed?

[sbenthall]

@llorracc : what about infinitessimally sized point masses for the endpoints?

[alanlujan91]

#todo for other distributions adding endpoints (truncated lognormal)