Fix docs: s3fs does not like dots in bucket names if your region is not us-east-1

[shntnu]

Reported by @mwawer

[mwawer]

s3fs will fail with: s3fs.cpp:s3fs_check_service(3813): unable to connect(host=https://s3.amazonaws.com) - result of checking service

For details, see: https://github.com/s3fs-fuse/s3fs-fuse/wiki/FAQ#q-https-connecting-failed-if-bucket-name-includes-dot-

[ErinWeisbart]

Added to documentation in #135.