make psycopg2 optional install, and add instructions on this
0.1.42
* openai_gpt.py catch non-retried exceptions to avoid crashing. * SQLAgent: improve prompt to do multi-step, retry, etc.
0.1.41
Improve TableChatAgent: * use table summary to avoid mistakes. * re-generate code if null/unexpected results or errors * answer questions using `run_code` in multiple steps.