0.4

• Better interface separation with clear functionality boundaries.
• Separated unit tests and integration tests.
• Removed set_link_conditioner from Socket
• Make last_sent sent with unreliable packets.
• Change allocations to iterators.
• Canonicalizes an "established connection" as requiring both a send and a receive from a given endpoint.
• Change SocketEvent::Connect to only fire when a connection has been established.
• Add SocketEvent::Disconnect to fire when a Timeout fires from an endpoint with an established connection.
• Change SocketEvent::Timeout to fire when a Timeout fires from an endpoint with an unestablished connection.
• Change heartbeats to only send after a connection has been established.
• Add a max_unestablished_connections config option to prevent connection memory overflow attack