refactor: apply code guidelines rules to stackdriver.ts file

Author: silva-fabio

packages/opencensus-core/package-lock.json

@@ -53,8 +53,10 @@
     "gts": "^0.5.4",
     "ncp": "^2.0.0",
     "google-cloud": "^0.57.0",
-    "googleapis": "27.0.0",
+    "googleapis": "^27.0.0",
+    "gts": "^0.5.1",
     "mocha": "^5.0.4",
+    "ncp": "^2.0.0",
     "ts-node": "^4.0.0",
     "typescript": "~2.6.1"
   },