Feature/continuous asr (#119)

* bugfix: background gather for speech-only should still kill audio on dtmf entry when dtmfBargein is true

* initial changes for continuous asr

* move properties under recognizer

* update drachtio-srf@4.5.1

* catch exception on destroy

lib/tasks/specs.json

@@ -477,7 +477,9 @@
       },
       "requestSnr": "boolean",
       "initialSpeechTimeoutMs": "number",
-      "azureServiceEndpoint": "string"
+      "azureServiceEndpoint": "string",
+      "asrDtmfTerminationDigit": "string",
+      "asrTimeout": "number"
     },
     "required": [
       "vendor"