Researched persistence, chose to just structure information into json
files using GSON, as the integration is quicker. changed the Saver class
to include the json structure onto its writer.
wrote a loader class for usernames from JSON;
wrote and tested the load user names class. Wrote a new method for
adding new usernames.
created a method to handle creation of user folders for each user.
created a method to create a folder if it does not exist.
refactored the constructor to call this method.
wrote test to check if folders are created for users.
wrote method for deleting a user.
Building on the delete user method, making sure the file system
associated is also removed.