README
Extract the domain name from a URL
Write a function that when given a URL as a string, parses out just the domain name and returns it as a string. For example:
domain_name("http://github.com/carbonfive/raygun") == "github"
domain_name("http://www.zombie-bites.com") == "zombie-bites"
domain_name("https://www.cnet.com") == "cnet"