Sets pickle protocol to highest

* package signing protocol is now set to highest. Tests show this to be about a 35% speed increase and there is increased probability of correctly pickling complex objects.

* also upped the protocol on the result database picklefield.

django_q/models.py

@@ -16,9 +16,9 @@ class Task(models.Model):
     name = models.CharField(max_length=100, editable=False)
     func = models.CharField(max_length=256)
     hook = models.CharField(max_length=256, null=True)
-    args = PickledObjectField(null=True)
-    kwargs = PickledObjectField(null=True)
-    result = PickledObjectField(null=True)
+    args = PickledObjectField(null=True, protocol=-1)
+    kwargs = PickledObjectField(null=True, protocol=-1)
+    result = PickledObjectField(null=True, protocol=-1)
     group = models.CharField(max_length=100, editable=False, null=True)
     started = models.DateTimeField(editable=False)
     stopped = models.DateTimeField(editable=False)

django_q/signing.py

@@ -37,7 +37,7 @@ class PickleSerializer(object):
 
     @staticmethod
     def dumps(obj):
-        return pickle.dumps(obj)
+        return pickle.dumps(obj, protocol=pickle.HIGHEST_PROTOCOL)
 
     @staticmethod
     def loads(data):