Test if post_proc is called during watch

hgetall uses post_proc to make a dictionary from the results, check if
it is called while two commands are sent when watching a key but before
starting the multi part of the transaction.
Check if multi has started when handling post_proc

If the connection is in a transaction but multi has not been called
yet, treat post_proc as we would without a transaction.
Commit / discard are only valid after MULTI.
Merge pull request #76 from voipro/fix-async-during-watch

Multiple queued commands during watch