palette_message: Message if palette doesn't have enough number of colors.
Description
A note to the user about not using the default color palette
when the number of factor levels is greater than 8, the maximum number of
colors allowed by "Dark2" palette from the RColorBrewer package.
Usage
palette_message(package, palette, min_length)
Arguments
package
Name of package from which the palette is desired as string
or symbol.