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.
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 graceful_shutdown_timeout

Conflicts:
	src/main/java/com/relayrides/pushy/apns/ApnsConnection.java
	src/main/java/com/relayrides/pushy/apns/ApnsConnectionConfiguration.java
Added still more clarifying comments.
Merge pull request #117 from relayrides/graceful_shutdown_timeout

Graceful shutdown timeouts