Cleanup Unused CargoMake functions

[webern]

          Acknowledging that you copied this from me... we should remove unused functions (unless you are sure you are going to use them later). 

This one feels unnecessary either way since it is easy enough to pass Vec::new(), or [] when you have no args. Also see below, I think IntoIter<Item = String> might work without the type annotation.

Originally posted by @webern in #97 (comment)

Definition of done:

When the CargoMake object does not have unused functions and does not need underscore prefixes to silence warnings.