Tolerate less messages in prepareToSimpleStmt

Here's a PR for the changes I talked about in #89, removing tolerance for a CommandComplete message after Parse + Describe + Sync.  As far as I can tell, this should not break any applications which were not broken already (i.e. experiencing symptoms of the client state not matching the server state).


This PR also includes a separate commit which removes tolerance for BindComplete in the same code path -- if we don't bind there, why do we tolerate such a response from the server?