Suggestion: use ! to indicate mutating functions

[digital-carver]

It looks like the remove_* functions and clean_text mutate their docx argument. If so, it would be useful and expected to follow the usual Julia convention of ending the function names in ! to indicate that they're mutating functions. So for eg. remove_puncts!(...), clean_text!(...), etc.

[Jcharis]

Thanks a lot @digital-carver. I appreciate this 😃