A WordPress plugin which rewrites media attachment URLs to S3.
This plugin requires that the constant S3_UPLOADS_BASE_URL is defined. This should be the base URL of the uploads
directory at S3, without a trailing slash.
Example to include in wp-config.php:
define('S3_UPLOADS_BASE_URL', 'https://s3-eu-west-1.amazonaws.com/bucketname/uploads');