Switch live to a BoolParameter

Instead of constructor argument

test/tasks/test_base.py

@@ -0,0 +1,11 @@
+from unittest import TestCase
+from datetime import datetime
+
+from metrik.tasks.base import MongoNoBackCreateTask
+
+
+class BaseTaskTest(TestCase):
+
+    def test_mongo_no_back_live_false(self):
+        task = MongoNoBackCreateTask(current_datetime=datetime.now())
+        assert not task.live