Make json a function call

Requests changed `json` to a function call a while ago (see http://docs.python-requests.org/en/latest/api/#migrating-to-1-x). I just made it into a function call locally, and it worked like a charm!

PS: Thanks a lot for this script, after the bitly security thing I wanted to grab my data and anonymize my account; this worked perfectly for grabbing my data.