Add tests

[ehashman]

This software is bad in the sense that it doesn't have tests. This is because testing is kind of hard! We would have to spin up a mock LDAP database and Kerberos realm every time we ran the tests to ensure they worked. So this isn't something we've looked into yet, but it would significantly improve the code and reliability.

Once we have tests and #7 is done, we could add code coverage tests as well.