Updated administrativia for safe_string.
Lwt_bytes: safe_string.
Lwt_chan: safe_string.
Lwt_unix: safe_string.
Lwt_io: safe_string.
Lwt_log: safe_string.
Lwt_process: safe_string.
Lwt_ssl: safe_string.
Lwt_simple_top: safe_string.
Added Lwt_unix.write_string, Lwt_io.write_from_string{,_exactly}.
Merge pull request #100 from vbmithr/safe_string

Be safe_string compatible.