FIX for max frame size handling
FIX for max frame size handling

Connection.frame_max limits the *total* frame size, including header and end
marker, which add up to 8 octets in total. Hence body fragmentation
should occur in chunks of frame_max-8.

stormed-amqp was sending frames that could be 8 octets too large.

bug reported by Matthias Radestock.

bufferx/stormed-amqp,paolo-losi/stormed-amqp