Add RDAP support

[phillip-stephens]

Uses open-rdap to query RDAP servers for each input IP.

Example Usage (from README)

$ echo "1.1.1.1" | ./zannotate --rdap 
{"ip":"1.1.1.1","whois":{"DecodeData":{},"Lang":"","Conformance":["history_version_0","nro_rdap_profile_0","cidr0","rdap_level_0"],"ObjectClassName":"ip network","Notices":[{"DecodeData":{},"Title":"Source","Type":"","Description":["Objects returned came from source","APNIC"],"Links":null},{"DecodeData":{},"Title":"Terms and Conditions","Type":"","Description":["This is the APNIC WHOIS Database query service. The objects are in RDAP format."],"Links":[{"DecodeData":{},"Value":"https://rdap.apnic.net/ip/1.1.1.1","Rel":"terms-of-service","Href":"http://www.apnic.net/db/dbcopyright.html","HrefLang":null,"Title":"","Media":"","Type":"text/html"}]},{"DecodeData":{},"Title":"Whois Inaccuracy Reporting","Type":"","Description":["If you see inaccuracies in the results, please visit: "],"Links":[{"DecodeData":{},"Value":"https://rdap.apnic.net/ip/1.1.1.1","Rel":"inaccuracy-report","Href":"https://www.apnic.net/manage-ip/using-whois/abuse-and-spamming/invalid-contact-form","HrefLang":null,"Title":"","Media":"","Type":"text/html"}]}],"Handle":"1.1.1.0 - 1.1.1.255","StartAddress":"1.1.1.0","EndAddress":"1.1.1.255","IPVersion":"v4","Name":"APNIC-LABS","Type":"ASSIGNED PORTABLE","Country":"AU",...

Associated Issues

Closes #5