Bot now stores comment ids in Heroku Postgres DB

This change was necessary because Heroku (specifically the Cedar stack,
which this bot runs on) uses an ephemeral file system, which then led to
commentids.p being emptied after each restart/stop of the worker dyno.
Postgres is a better option anyway.
Added psycopg2 to requirements.txt
Fixed command parsing issues, added info footer
Add required SQL file for executing on Postgres
Add empty tmp.txt (used for searching database)