Parse returns "invalid" if referrer url netloc is a valid IP address

[kmbibic]

Currently, Referrer.parse returns type: "invalid" if the netlocation of the referrer URL is a valid IP address. Referrers like this are definitely valid, so in places where Referrer.parse is being used, we have to check for valid IP addresses in the netloc and explicitly set the type to "indirect" instead of "invalid" which isn't ideal.

For example:

url = "http://108.61.207.249/ga.php"
ref = Referrer.parse(url)
parsed_url = urlparse(url)

ref shows a type: "invalid", but if we run IP(parsed_url.netloc) (where IP is from IPy) and see that the IP address is valid and the referrer shouldn't be tagged as "invalid". As a result, we have to explicitly check for this case and overwrite the type to "indirect" when using Referrer.parse().

cc @CamDavidsonPilon