Expand options for CloudSQL Proxy

[marcusvb]

The following page in the gmemegen tutorial assumes the user is running linux.amd64. See the wget command.

wget https://dl.google.com/cloudsql/cloud_sql_proxy.linux.amd64 -O cloud_sql_proxy

Instead I suggest to replace that block with the multi-option Cloud SQL Proxy download found on your cloud platform. The one provides multiple commands based on the user's OS.