Add js-data-schema integration

[jmdobry]

If js-data-schema is loaded the default validate lifecycle hook will change from a noop to a function that validates an item against a resource's schema if the developer defines one. Example:

var User = store.defineResource({
  name: 'user',
  schema: {
    name: {
      type: 'string',
      nullable: false
    },
    id: {
      type: 'string',
      nullable: true
    }
  }
});