Added a `closeAfterInactivityTime` option to channel config objects. Doesn't have teeth yet.
Added a handler that will close connections if they're idle for a prescribed amount of time.
Removed a spurious block in a test.
Added `gracefulShutdownTimeout` to `ApnsConnectionConfiguration`.
Added support for shutting down immediately if a graceful shutdown attempt times out. Still need to add tests.
Added a test for graceful shutdown timeouts.
Trigger a write failure if we know the connection is shutting down.
Added a send attempt limit option to ApnsConnectionConfiguration.
Merge branch 'close_connections_when_inactive' of github.com:relayrides/pushy into close_after_send_attempt_limit

Conflicts:
	src/main/java/com/relayrides/pushy/apns/ApnsConnection.java
	src/main/java/com/relayrides/pushy/apns/ApnsConnectionConfiguration.java
Added shut-down-after-send-attempt-limit functionality and tests.
Merge branch 'master' of github.com:relayrides/pushy into close_connections_when_inactive
Merge branch 'close_connections_when_inactive' of github.com:relayrides/pushy into close_after_send_attempt_limit
Fixed a copy constructor goof and updated tests accordingly.
Added a clarifying comment.
Merge branch 'close_connections_when_inactive' of github.com:relayrides/pushy into graceful_shutdown_timeout
Fixed more copy constructor mistakes and added some clarifying comments to tests.
Merge branch 'close_connections_when_inactive' of github.com:relayrides/pushy into close_after_send_attempt_limit
Fixed a spelling error.
Added an explicit check for null configurations in the ApnsConnection constructor.
Let us never speak of this again.