lib/classes/Variables.js/Variables/populateVariables
class Variables:  populateVariables(properties) {
    const variables = properties.filter(
      property => _.isString(property.value) && property.value.match(this.variableSyntax)
    );
    return _.map(variables, variable =>
      this.populateValue(variable.value, false).then(populated =>
        _.assign({}, variable, { populated })
      )
    );
  }