remove bank_accounts and credit_cards tables

These some how have stuck around in the schema after being renamed.
On production, we have all the old account information, and the
tables don't exisit. Deleting them is to make sure anyone who might
clone this repository doesn't get unneeded tables in their database.
Merge pull request #60 from epicodus/remove-tables-from-schema

remove bank_accounts and credit_cards tables