add new emails to disposable yml list

@maj @vanpelt @cchanningallen , there are two places we should be validating emails.  This fulfills the server side validation.  It has been tested locally.

I am not 100% sure if this is the correct way to version a gem, though.
I think this is business-specific logic not applicable to the general public. This project should be privatized or the list of emails should be set by the parent app.