accept timestamp as opt in erlang_syslog:send/3
use Z instead of +00:00 for timezone offset
proper syslog RFC5424 format

RFC5424 has split the TAG field into APP-NAME, PROCID, and MSGID. The
app_name option is now required at init, but can be overridden on a
per-message basis.
add hostname option
readme updates for rfc5424/rfc5426 format