Shortcuts for options(s3pe.bucket = ) and options(s3pe.endpoint = ):
after use_bucket("my-bucket") every verb accepts bare keys
(read_s3("data/manifest.json")); after
use_endpoint("https://s3.example.org") requests go to that store for
the rest of the session. NULL clears the setting.
Examples
if (FALSE) { # interactive()
use_endpoint("https://s3.example.org")
use_bucket("my-bucket")
read_s3("data/manifest.json")
}