When running the tests on Node v0.10, setup `global.Promise`
with Bluebird implementation. That way we don't have to run
this setup in the test suite of each kv connector.
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);