This is a breaking change. Juggler methods are no longer returning
instances of Bluebird Promise, but return a native Promise instead.
As a result, API consumers can no longer use sugar APIs provided by
Bluebird, e.g. `spread`, `delay`, etc.
Migration guide: rewrite your code from `.then()` style into `async`
functions using `await` statements.
Models attached to a KeyValue connector get the following *static*
methods:
Color.set(key, value);
Color.set(key, value, ttl);
Color.set(key, value, { ttl: ttl });
Color.get(key);
Color.expire(key, ttl);