Converts this hostname to lower case.
(hostname: Ordered[Hostname]).<(that)
(hostname: Ordered[Hostname]).<=(that)
(hostname: Ordered[Hostname]).>(that)
(hostname: Ordered[Hostname]).>=(that)
(hostname: Ordered[Hostname]).compare(that)
(hostname: Ordered[Hostname]).compareTo(that)
RFC1123 compliant hostname.
A hostname contains one or more labels, where each label consists of letters A-Z, a-z, digits 0-9, or a dash. A label may not start or end in a dash and may not exceed 63 characters in length. Labels are separated by periods and the overall hostname must not exceed 253 characters in length.