q.d: interactive debugging

Hi Ping,
   My name's Dan Lepage - we spoke briefly at PyCon, and I requested a feature in q to launch an interactive shell from any point in the code. Here's a patch that adds it! In addition to launching a shell, it will log "Interactive Prompt Opened" and "Interactive Prompt Closed", and info shown from q directly from the prompt will show the function name as &lt;prompt&gt; instead of &lt;module&gt;.

Thanks!
Dan