Basic budget management

[Jnesselr]

The goal for this was to lay the groundwork for our automated budget management systems. I've introduced the Budget and StripeCard models. StripeCard is currently set to sync hourly. That entire table gets updated from Stripe's API. Originally this was just to backfill the data, but it may prove useful to always get new cards this way as well.

The Budget class has no UI as of yet. We have a few options there:

• We could manually update these (ie I teach @Agent123983 how to access the command line interface and build these budget objects).
• We essentially don't do anything based on budgets yet. (keep our top-up at $1k, and don't adjust spending limits)

Next chunks of work (approximately in order):

• UI/UX for @Agent123983 in Slack
• QuickBooks integration (adjusting parent class depending on if the budget is active or not)
• Basic transactions support (Basically a model for transactions done on the stripe cards. End goal will be to take transactions into account when setting issuing balance for a given card as well as sending a message in Slack when we get a new transaction in.)
• More complete transaction flow (TBD all the details, but essentially trying to make it easier to do things like attach receipts)
• Improve flow for getting people set up with Stripe (Up to this point, we'd need to make the cardholder and cards manually and THEN create the budget against those cards. So the Slack UI/UX might change at this point. We also need to handle all the nonsense like "are we sending this card to the right address" and "here's how you activate the card" and such.)
• Support more than just "budget is attached to person with physical card"