SMTP: don't create new Transaction at disconnect

the current result of passing a DENY* response is a new transaction. That seems wrong.
Merge pull request #106 from msimerson/disconnect

SMTP: don't create new Transaction at disconnect
Q::hooks(), accept a hook name argument

and return a useful result
Merge pull request #108 from msimerson/hooks

Q::hooks(), accept a hook name argument
updated MANIFEST

adding t/config/users.cdb (goes with closed PR #102)
Merge pull request #109 from msimerson/master

updated MANIFEST
qpsmtpd.t: added tests for hook_responder
Qpsmtpd: style changes in hook_responder
added test for run_continuation