Added first test for REGISTERING
Add test for wrong password, forces user lookup
Add test for brewing with right password
Add test for deregistration with wrong password
Add test for deregistering user (remove from users.db)
Add test for existence in user db
Add test to check that USER can not be overwritten
Refactor register command
Refactor brewing command
Refactor deregister
Add negative testcase for taking a brewed coffee
Add negative test - there is nothing brewing for this user
Add FAILING check in test that user has something brewed