Initializes bookshelfModel's toJSON functionality to convert all date properties, as defined in bookshelfModel.schema.
function initJsonDateFormat (bookshelfModel) {
  const schema = bookshelfModel.prototype.schema
  const originalFunction = bookshelfModel.prototype.toJSON
  // read from MySQL date, based on https://github.com/tgriesser/bookshelf/issues/246#issuecomment-35498066
  bookshelfModel.prototype.toJSON = function () {
    const attrs = originalFunction.apply(this, arguments)
    _.forEach(attrs, function(v, k) {
      if (v !== null && typeof schema[k] !== 'undefined' && schema[k]._type === 'date') {
        attrs[k] = moment(v).format(schema[k]._flags.format)
      }
    })
    return attrs
  }
}