Add automatic deregistration option

[zhanazhan]

Added deregistration option when service is failing, greatly helps when service was killed with -9 option.

If you guys want to update Registration class, here is the change.

Registration.java.txt

[jplock]

Do we need to add https://github.com/OrbitzWorldwide/consul-client/pull/168 in another spot?

[rickfast]

Make a PR and I'll merge it

[alugowski]

This already exists. Consul keeps track of this timer for health checks, not service instances. You can add a deregisterCriticalServiceAfter to any health check:

Registration.RegCheck deadManSwitch = ImmutableRegCheck.builder()
		.ttl("10s")
		.deregisterCriticalServiceAfter("3h")
		.build();