Standardized output types for multi_predict and predict in multinom_reg

[patr1ckm]

Fixes #222 .

[codecov-io]

Codecov Report

Merging #226 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #226   +/-   ##
=======================================
  Coverage   76.32%   76.32%           
=======================================
  Files          38       38           
  Lines        2995     2995           
=======================================
  Hits         2286     2286           
  Misses        709      709

Impacted Files	Coverage Δ
R/multinom_reg.R	79.09% <100%> (ø)	⬆️

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[topepo]

In multinom_reg.R, please add the levels to the factor call. If we only predict a single level, the factor levels won't be correct.

[topepo]

Thanks for these PRs. We are about to do a release so the timing is perfect.

[github-actions]

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