Buffering now takes the pending bytes on the socket into account (when present) rather than relying entirely on select(). In some instances the final bytes would not be flushed until the connection was closed.
Refactor storage layer to allow for new repository filesystems using drivers. (Reviewed by Cynthia Shang.)
Refactor IO layer to allow for new compression formats, checksum types, and other capabilities using filters. (Reviewed by Cynthia Shang.)
