Release v0.28.0 (#539)

Author: callmehiphop

handwritten/pubsub/samples/package.json

@@ -14,7 +14,7 @@
     "test": "mocha system-test --timeout 600000"
   },
   "dependencies": {
-    "@google-cloud/pubsub": "^0.27.1",
+    "@google-cloud/pubsub": "^0.28.0",
     "yargs": "^13.0.0"
   },
   "devDependencies": {