Add min_ttl and max_ttl to the Host class and ttl to the ICMPReply class

[joente]

The TTL properties are missing when preforming a ping (or async_ping)

Added a min_ttl and max_ttl property to the Host class which is filled from a new ttl property on the ICMPReply class.

In this version it only works for IPv4 which is enough most of the time although we could search for an implementation for IPv6 as well. (this version would return 0 for both min- and max_ttl when using an IPv6 address.

[ValentinBELYN]

Hi @joente,

Thanks for this PR. Although I find the interest of the TTL limited (there have already been several requests on this subject), I will however think about it for future versions. With icmplib, I try to have a parity between the features available between IPv4 and IPv6.