Add minimum_confidence option

Now setting the minimum_confidence option in options.json allows the
user to control the minimum confidence a plugin must have to be executed
at all.  A value of null (the default) means all values greater than
zero are accepted.  All other values mean all confidences greater than
or equal to that value are accepted.

kayleevc/conf/options.json

@@ -5,5 +5,6 @@
     "interface": null,
     "valid_sentence_command": null,
     "invalid_sentence_command": null,
-    "tts": ["espeak", "-ven-us+f2"]
+    "tts": ["espeak", "-ven-us+f2"],
+    "minimum_confidence": null
 }

kayleevc/kaylee.py

@@ -140,14 +140,16 @@ class Kaylee:
 
     def recognizer_finished(self, recognizer, text):
         confidence_heap = queue.PriorityQueue()
+        min_confidence = self.options['minimum_confidence']
         # Add plugins to the heap
         for index, plugin in enumerate(self.plugins):
             # Get plugin confidence
             confidence = plugin.confidence(text)
             # Clamp confidence to [0, 1]
             confidence = min(max(confidence, 0), 1)
-            # TODO: Only add items if they meet minimum confidence
-            if confidence > 0:
+            # If the plugin meets minimum confidence
+            if ((min_confidence is not None and confidence >= min_confidence)
+                or (min_confidence is None and confidence > 0)):
                 # Add a triple to the heap, so plugins are sorted first by
                 # confidence, then by index to break ties
                 confidence_heap.put_nowait((1 - confidence, index, plugin))