Refactor spec to check presence of record on page

Instead of interacting with the database to determine if a record has
been created (outside the scope of what a user interacting via a browser
would be able to do usually), verify the record is on the page in the correct
location.
Extract random username generator

This extracts the logic for generating a random username to an
Anonymizer class which allows injection of both adjective and noun lists
as well as a max random number.