Description

Refactored specified function names in R/plotme.R based on issue #7

Original	Modified	User Facing
count_to_sunburst	plotSunburst	✅
count_to_treemap	plotTreemap	✅
create_all_col_params	prepareColumnParams	✅
create_one_col_params	prepareSingleColumnParams	✅
assert_count_df	validateCountDF	✅
all_non_n_cols_to_char	.all_non_n_cols_to_char

Fixes issue #50

What kind of change(s) are included?

[ ] Feature (adds or updates new capabilities)
[x] Bug fix (fixes an issue).
[ ] Enhancement (adds functionality).
[ ] Breaking change (these changes would cause existing functionality to not work as expected).

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[x] I have performed a self-review of these additions (including spelling, grammar, and related).
[x] I have added comments to my code to help provide understanding.
[x] I have added a test which covers the code changes found within this PR.
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