Add testing dependency

This commit adds a dependency for nose to pip.req. It also renames the "test"
script to "test_ldap.py" to make room for the unit tests directory.
Add sample unit test skeleton

test/test_authenticate.py is a sample nosetests skeleton. A live version should
have hard-coded NetID and password attempts that test for both success and
failure. As these have secrets, the final version should not be committed to the
repository.
Merge pull request #5 from ksuarz/feature/test

Unit test skeleton