Add assumed state for Tellstick devices.

Tellstick device states are always assumed so this should be set to true.

homeassistant/components/light/tellstick.py

@@ -125,3 +125,8 @@ class TellstickLight(Light):
     def should_poll(self):
         """ Tells Home Assistant not to poll this entity. """
         return False
+
+    @property
+    def assumed_state(self):
+        """  Tellstick devices are always assumed state """
+        return True

homeassistant/components/switch/tellstick.py

@@ -72,6 +72,11 @@ class TellstickSwitchDevice(ToggleEntity):
         """ Tells Home Assistant not to poll this entity. """
         return False
 
+    @property
+    def assumed_state(self):
+        """  Tellstick devices are always assumed state """
+        return True
+
     @property
     def name(self):
         """ Returns the name of the switch if any. """