Fix json decoding on Python 3

Related to #36 -- there exists a much easier solution to the approach taken there, that is just relying on the `requests` library to decode the json (the Python 2/3 difference is dealt with there already).

How can the current implementation even pass the tests on Python 3? The `get_database_list` CAN'T possibly work on Python 3 because it wasn't taken care of in #36.
That's not correct. http://docs.python-requests.org/en/latest/user/quickstart/#json-response-content