Use Host instead of Hostname for Session creation

[keynmol]

Hostname is not capable of parsing IPV6 addresses:

scala> Hostname.fromString("127.0.0.1")
val res0: Option[com.comcast.ip4s.Hostname] = Some(127.0.0.1)

scala> Host.fromString("127.0.0.1")
val res1: Option[com.comcast.ip4s.Host] = Some(127.0.0.1)

scala> res1.map(_.getClass.getName)
val res2: Option[String] = Some(com.comcast.ip4s.Ipv4Address)

scala> Hostname.fromString("::1")
val res0: Option[com.comcast.ip4s.Hostname] = None

scala> Host.fromString("::1")
val res1: Option[com.comcast.ip4s.Host] = Some(::1)

(repl sessh courtesy of @mpilquist )

[mpilquist]

Thanks! Can we target series/0.6 instead of main?

[keynmol]

Done

[keynmol]

I can backport it to main to eventually get a 1.x milestone with it