Refactor the generate colors functions to own library

Move the logic which generates the colors to its own library.  This
helps with testing and makes a bit more sense in how we export the
functions.

We must also include this new directory in the scripts for test within
the package.json file.
Expand on API test, add rewire

Using rewire, expand on the API test to verify the text is sent to the
colors service, the return of which is sent to the user.
Add tests for the generate color functions

Add tests for both the generateColor and generateColors functions.  Add
a null check for the generateColors function, include some comments.