The date validator has a different allowBlank validation

[frykten]

Hi! 👋

While working with ember-changeset-validations, which uses this addon quite extensively, I saw there was an "inconsistency" in the behaviour of the date validator's allowBlank option, which checks nullish values and empty strings instead of using Ember's util isEmpty, as per all other validators (cf.).
I also saw that was introduced when removing Moment (cf. commit). Was it meant to be?