Connection required on initialization

When instantiating a `GitHub::Ldap` object, a connection is established and query performed to determine the server's capabilities which are used to configure the appropriate membership search strategies.

I'd like to avoid having to connect and query on object instantiation and only perform the query when it's absolutely needed.

Start at GitHub::Ldap object initialization and trace the connection and server-capability query that selects membership search strategies. Determine which operations actually require those capabilities, then verify that initialization avoids the connection while needed membership searches still obtain the correct strategy and query the server.

Written by the indexing model from the issue text.