Right now Advanced Custom Fields are not supported for get requests out of the box. Until the ACF developer builds WP-API support, field data must be embedded manually.
ACF get_fields() data is merged into the meta response through a json filter.
Put this plugin in your wordpress plugins folder.
WP JSON Rest API: https://github.com/WP-API/WP-API Advanced Custom Fields: http://www.advancedcustomfields.com