Add parser test for split messages.
Add parser test for split messages.

Note: it seems that the parser code coverage in the client is not that
great. Since the code is common in part with the server, we know that
this code is tested, but wonder if we need to duplicate tests existing
in the server.

apcera/nats,wallyqs/go-nats,wallyqs/go-nats,nats-io/go-nats,apcera/nats,nats-io/nats,ZebinKang/go-nats,nats-io/go-nats,nats-io/nats,ZebinKang/go-nats,pires/nats,pires/nats