Stub of Tea Time model. Very basic
Stub the User model so it may be used in relationships
Create basic relationship structure

Between:

* Cities and Tea Times
* Tea Times and Hosts
* Tea Times and Attendees

This also creates a stub of the user model.
Init and Sync DB on server start
cityAPI get and post routes
Modularise controllers folder & add City

* Create controllers folder+index
* Move cityAPI into controllers/cities.js
* Make all responses from server default to JSON with addition of new response
  filter
Add models to the `req` object

As originally exported from the DB object, models were under their own
properties, e.g. 'City', 'TeaTime', etc.  This moves them onto the `models`
property.
Merge pull request #17 from TeaWithStrangers/teatime-basics

City API with Creation and Retrieval of all City objects