Type fixes for Postgres 8.x (we noticed issues on 8.3. Newer versions of Postgres don't auto massage integers from Python to string values in the database. In Bitten, this was causing issues with the 'id' field of bitten_rule, which was actually an integer (coming from the id field of the bitten_platform table.) Without explicitly converting it to a string, you'd see the error reported in #390. Added upgrade steps, tested on Postgres8.3. Closes #390. We may want to rename this field to 'platform' later.