add Server::TCP#stop spec
Server#stop: stop ALL the servers!
factor out Server::UDP#run_select_loop
Server::UDP.new: require port
Server::UDP spec: standardise on port 1979
Server::UDP: move binding to #start
Server::TCP spec: allow the server to close
Server::UDP spec: minor naming clarification
Server::TCP.new: require port
Server::TCP spec: standardise on port 1981
Server::HTTP: require port
Server::UDP.new: take an Addr
simplify Server::UDP#addr spec
simplify Server::UDP#stop spec
simplify Server::UDP logging spec
Server::TCP.new: take an Addr
simplify Server::TCP#addr spec
simplify Server::TCP#stop spec
simplify Server::TCP logging spec
Server::HTTP.new: take an Addr