zarr anonymous s3 access

[fcollman]

I can't get cloud-volume to read a zarr array in a public bucket because there is no way to force it to not sign requests. The option is there in cloud-files but there is no way to pass the "no_sign_request=True" option down to cloudfiles.

[william-silversmith]

I see... so when it's s3 and https, we need to pass in no sign requests.