Feature/gather enhancements (#73)

* add bargein support to gather

* bugfix: gather handles interim results from azure

* gather: support for min/max digits and interdigit timeout

* add task summary to some log messages

* logging improvements

lib/tasks/specs.json

@@ -98,8 +98,15 @@
       "finishOnKey": "string",
       "input": "array",
       "numDigits": "number",
+      "minDigits": "number",
+      "maxDigits": "number",
+      "interDigitTimeout": "number",
       "partialResultHook": "object|string",
       "speechTimeout": "number",
+      "listenDuringPrompt": "boolean",
+      "dtmfBargein": "boolean",
+      "bargein": "boolean",
+      "minBargeinWordCount": "number",
       "timeout": "number",
       "recognizer": "#recognizer",
       "play": "#play",