Integrate with mockldap for tests, instead of real LDAP server

MockLDAP is a mock replacement for python-ldap. It's useful for any project
that would like to write unit tests against LDAP code without relying on a
running LDAP server.

Links:
https://pypi.python.org/pypi/mockldap
http://pythonhosted.org//mockldap
update travis to switch away from the real LDAP server and use mockldap instead
Merge pull request #17 from tampakrap/mockldap

Integrate with mockldap