Refactored code to clean up logic

Created two new model classes -> users and pairs. This allows for easier
management of the two concepts instead of master race class db. Many
things are still not implemented, but a lot of the cleanup work has been
done.

TO-DO:
- Reimplement twilio sending
- Reimplement pce
- Probably actually test the code
- Implement oy as well
- Currently not unsetting is_paired flag in user table
Removing db.js
Reorder db initialization
Merge pull request #2 from ericluii/callback-magic

Callback magic