Added docstring for update_context

Including note about not working on one_of keywords.

mycroft/skills/intent_service.py

@@ -180,6 +180,16 @@ class IntentService(object):
         self.active_skills.insert(0, [skill_id, time.time()])
 
     def update_context(self, intent):
+        """
+            updates context with keyword from the intent.
+
+            NOTE: This method currently won't handle one_of intent keywords
+                  since it's not using quite the same format as other intent
+                  keywords. This is under investigation in adapt, PR pending.
+
+            Args:
+                intent: Intent to scan for keywords
+        """
         for tag in intent['__tags__']:
             if 'entities' not in tag:
                 continue