allow for 'color' kwarg to be passed as a plot argument in annotate_clumps

[munkm]

This resolves #1896.

If color is included in the plot_args dictionary it is now changed to colors and the behavior in annotate_clumps() is consistent with other annotate_ functions. Previously, passing color did nothing if passed as as a plot argument through annotate_clumps().

• Code passes flake8 checker
• New features are documented, with docstrings and narrative docs
• Adds a test for any bugs fixed. Adds tests for new features.