Added Cache-Control response headers to prevent ID caching
Added a health check /ping endpoint and a /version to print the Snowizard version
Added an option to validate the User-Agent header or not
Fixed failing unit test after adding PingResource and SnowizardResource
Code formatting
Added an option to return CORS response headers or not. If you have no intention of accessing Snowizard from a browser, you can safely disable this to reduce the response size.