Require socket

when loading mimic, you get the following error:

/Users/hubert/.rbenv/versions/1.9.3-p448/gemsets/comptroller/gems/mimic-0.4.3/lib/mimic.rb:89:in `rescue in listening?': uninitialized constant Mimic::Server::SocketError (NameError)

requiring socket explicitly in mimic.rb takes care of it.