Update dependency google/cloud-tools to v0.12.0

Author: renovate[bot]

docs/samples/composer.json

@@ -4,7 +4,7 @@
         "duncan3dc/cache": "~0.4"
     },
     "require-dev": {
-        "google/cloud-tools": "^0.8",
+        "google/cloud-tools": "0.12.0",
         "phpunit/phpunit": "~5"
     }
 }