BigQuery: update quickstart to latest package versions.

Version 0.3.1 is the latest version of the google/cloud-bigquery package.

It includes some breaking changes, so the api samples will need to be updated separately.

Author: tswast

bigquery/quickstart/composer.json

@@ -1,7 +1,7 @@
 {
     "require": {
         "php": ">=5.4",
-        "google/cloud-bigquery": "^0.2"
+        "google/cloud-bigquery": "^0.3"
     },
     "require-dev": {
         "phpunit/phpunit": "~4"