Fix 413 response from Discourse due to empty dict passed as json

pydiscourse/client.py

@@ -949,7 +949,7 @@ class DiscourseClient(object):
         """
         Get all infos of a group by group name
         """
-        return self._get("/groups/{0}/members.json".format(group_name))
+        return self._get("/groups/{0}.json".format(group_name))
 
     def create_group(
         self,
@@ -1357,10 +1357,6 @@ class DiscourseClient(object):
             dictionary of response body data or None
 
         """
-        params = params or {}
-        files = files or {}
-        data = data or {}
-        json = json or {}
         override_request_kwargs = override_request_kwargs or {}
 
         url = self.host + path