POE::Component::Client::Ping is non-blocking ICMP ping client. It lets
several other sessions ping through it in parallel, and it lets them
continue doing other things while they wait for responses.

Ping client components are not proper objects. Instead of being created, as
most objects are, they are "spawned" as separate sessions. To avoid
confusion (and hopefully not cause other confusion), they must be spawned
with a 'spawn' method, not created anew with a 'new' one.

PoCo::Client::Ping's 'spawn' method takes a few named parameters: