Fix eta facet names inaccurate grouping (#144)

[billdenney]

This replaces PR #145 and fixes #144 (updated to the new master and removed a pesky commit that was inaccurately in the last version)

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@f2bbab5). Click here to learn what that means.
The diff coverage is 100%.

@@           Coverage Diff            @@
##             master    #151   +/-   ##
========================================
  Coverage          ?   94.4%           
========================================
  Files             ?      40           
  Lines             ?    3055           
  Branches          ?       0           
========================================
  Hits              ?    2884           
  Misses            ?     171           
  Partials          ?       0

Impacted Files	Coverage Δ
R/plot_distribution.R	93.47% <100%> (ø)

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[billdenney]

@guiastrennec, I've rebased this to dev for easier pulling.