Write MySQL data schema

[cmcavoy]

SQL To-Do

List of models to convert to SQL schemas.

Marking them complete if I have at least a first pass at them.

• [x] badge class
• [x] badge instance
• [x] tag
• [x] tag to badge class map
• [x] user
• [x] claim code
• [ ] issuer
• [ ] program
• [x] behavior