code: function fmt(str){
    var args = [].slice.call(arguments, 1);
    var j = 0;
  
    return str.replace(/%([a-z])/gi, function(_, f){
      return fmt[f]
        ? fmt[f](args[j++])
        : _ + f;
    });
  }
docs: Format the given `str`.
  
  @param {String} str
  @param {...} args
  @return {String}
  @api public