fix(deps): use the latest extend (#529)

Author: JustinBeckwith

package.json

@@ -56,7 +56,7 @@
     "concat-stream": "^2.0.0",
     "dot-prop": "^5.0.0",
     "escape-string-regexp": "^2.0.0",
-    "extend": "^3.0.0",
+    "extend": "^3.0.2",
     "google-auth-library": "^5.0.0",
     "google-gax": "^1.0.0",
     "is": "^3.0.1",