IPv4 range 240/8-255/8 missing from patterns.go URLIP regexp

[dougparrish]

govalidator.IsURL("http://251.18.58.189:7979/my/path") returns false, even though the IP address is valid though "Reserved for future use" according to IANA[0]. Users are starting to use this [formerly Class E] range as a range for a fan network[1].

[0] https://www.iana.org/assignments/ipv4-address-space/ipv4-address-space.xhtml

[1] Excerpt from https://wiki.ubuntu.com/FanNetworking:
"The Future Use range (240.0.0.0/8 through 255.0.0.0/8) is a particularly good set of IP addresses you might use, because most routers won't route it..."