Broadcast custom_json with active authority

* custom_json with required_auths are now broadcasted with active key
* json field in custom_json is broadcasted compact (spaces are removed)

beem/steem.py

@@ -1604,7 +1604,10 @@ class Steem(object):
                 "id": id,
                 "prefix": self.prefix,
             })
-        return self.finalizeOp(op, account, "posting", **kwargs)
+        if len(required_auths) > 0:
+            return self.finalizeOp(op, account, "active", **kwargs)
+        else:
+            return self.finalizeOp(op, account, "posting", **kwargs)
 
     def post(self,
              title,

beembase/operations.py

@@ -394,7 +394,7 @@ class Custom_json(GrapheneObject):
             kwargs = args[0]
         if "json" in kwargs and kwargs["json"]:
             if (isinstance(kwargs["json"], dict) or isinstance(kwargs["json"], list)):
-                js = json.dumps(kwargs["json"])
+                js = json.dumps(kwargs["json"], separators=(',',':'))
             else:
                 js = kwargs["json"]