A user should be able to permanently store and access their bank data

[emoseswustl]

Current outline:

• [ ] Look for file(s) with specified names in directory
• [ ] If file exists, read in objects from file and store them (should be user and account classes), give user access to main menu
• [ ] If file does not exist, create blank file and skip reading, give user the option to create an account, write user acct to file
• [ ] Write to file as actions are taken (update account balances, etc.)
• [ ] On exit, make sure files are taken care of (closed if needed)