Use .env to specify different S3 buckets for puzzle thumbnails

[luxaritas]

Currently we hardcode it to our production website bucket. At the least this value should be able to be set via the .env (and have our provisioning code handle creating a .env.local to set it appropriately). Might be nice to automatically pick up on changing the remote url from eternagame to eternadev and switch it automatically? Or have some sort of variable that will automatically change both at once for development purposes or something. TBD