Laid the groundwork for cancelling in-progress connection attempts. Tests are (correctly) failing at this point.
Made shutdown behavior more robust; we now close connections regardless of where they are in the connection process.
Updated to Netty 4.0.18, which resolves connection cancellation warnings.
Stored handshake completion as a boolean rather than re-checking the status of a future. Seems worth simplifying since it happens in `sendNotification`.
Merge pull request #59 from relayrides/cancel_connection_attempt

Cancel in-progress connection attempts (fixes #58)