Added separator option for output path and module arrays

Allow users to specify the separator (`' '`, `'\n'`, `'\n\t'`, etc) they would like to use between elements of the output arrays for modules and paths in the optimized content. Defaults to empty space (`' '`) so original behavior is not modified if this option is not supplied.

Also added documentation for this option to `README.md`.

**NOTE** I did not update package versions, etc.