Use the much fancier url-regex

Scraps the existing regex in favor of https://github.com/kevva/url-regex, per @sindresorhus's suggestion. Because the new regex is more permissive, schemeless strings like `google.com` are considered to be URLS. This is a breaking change, so I'm thinking of shipping this as 2.0.0.
FYI, I might add a `strict` option to `url-regex` to allow for local IPs etc when setting it to `false`.