docs: function(message, line, col, rule, data) {
          "use strict";
          var err = {
              type    : "error",
              line    : line,
              col     : col,
              message : message,
              evidence: this.lines[line-1],
              rule    : rule || {}
          };
          if (data) {
          	err.data = data;
          }
          this.messages.push(err);
      }