support bucket-in-hostname

[gaul]

S3Proxy supports bucket-in-path URLs, e.g., example.com/bucket-name/blob-name. It should also support bucket-in-hostname URLs, e.g., bucket-name.example.com/blob-name.

[mafrosis]

+1 would be very useful to see what's in my S3 proxy bucket with s3cmd :D

[gaul]

s3cmd 1.5.0 supports bucket-in-path, see s3tools/s3cmd#375 and s3tools/s3cmd#416.