Test the client, API improvements

[mbabker]

Pull Request for Issue #6

Summary of Changes

• Adds a functional test class covering the LdapClient
• Adds tracking state to make sure the connection is bound
• Adds a destructor to make sure the connection is closed when the object destroyed
• Adds checks to make sure the connection is established and bound when needed since we cannot lazy bind

Testing Instructions

Either put some trust in a green CI build or try to set up a LDAP server and use the client