When calling `deprecate` you must provide `for` in options. Missing options.for in "ember-moment.addon.helpers.moment-to-now" deprecation

Hello,
I'm getting this warning when using the `moment-to-now` helper.

It seems like [this deprecate](https://github.com/stefanpenner/ember-moment/blob/master/addon/helpers/moment-to-now.js#L9) should have a `for` option.

[According to the code of the `deprecate` method](https://github.com/emberjs/ember.js/blob/master/packages/@ember/debug/lib/deprecate.ts#L195) _options.for A namespace for the deprecation, usually the package name_

Would also be fixed by merging #338