support JSON response from auth, token endpoints

For example, the micropub.rocks auth endpoint only returns JSON-encoded responses.

This implementation wraps all top-level values in the JSON object in an array to match the behavior of `parse_qs` but does not check to see if the value is already an array.

flask_micropub.py

@@ -206,6 +206,9 @@ class MicropubClient:
             'Flask-Micropub: auth response: %d - %s', response.status_code,
             response.text)
 
+        try:
+            rdata = dict((k,[v]) for (k,v) in response.json().items())
+        except ValueError:
             rdata = parse_qs(response.text)
         if response.status_code < 200 or response.status_code >= 300:
             error_vals = rdata.get('error')
@@ -276,6 +279,9 @@ class MicropubClient:
                 error='bad response from token endpoint: {}'
                 .format(token_response))
 
+        try:
+            tdata = dict((k,[v]) for (k,v) in token_response.json().items())
+        except ValueError:
             tdata = parse_qs(token_response.text)
         if 'access_token' not in tdata:
             return AuthResponse(