Merge pull request #51 from yamt/multipart-fix

fix the value of multipart "more" flag
remove a questional error handling

as our underlying transport (tcp/ssl) is a stream which doesn't preserve
message boundaries, dropping an unparsable segment likely make the
situation worse.
fix message header parsing

if not enough bytes of data are available, return {error, binary_too_small}
so that the caller can retry when more data come.  it's normal as
our underlying transport (tcp etc) does not preserve message boundaries.
remove unused ofp_action_set_queue.port