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.
The new version of our config enabled function-paren-newline rule,
this commit fixes the codebase to use more consistent handling
of newlines when calling functions.
Support both promise and callback styles in
ModelBaseClass.notifyObserversOf.
When there is no callback supplied, the method returns a promise that
is resolved (or rejected) with the result.