vendors/tempy.js/range
    function range(a, b, str) {
      var begs, beg, left, right, result;
      var ai = str.indexOf(a);
      var bi = str.indexOf(b, ai + 1);
      var i = ai;
      if (ai >= 0 && bi > 0) {
        if (a === b) {
          return [ai, bi];
        }
        begs = [];
        left = str.length;
        while (i >= 0 && !result) {
          if (i == ai) {
            begs.push(i);
            ai = str.indexOf(a, i + 1);
          } else if (begs.length == 1) {
            result = [begs.pop(), bi];
          } else {
            beg = begs.pop();
            if (beg < left) {
              left = beg;
              right = bi;
            }
            bi = str.indexOf(b, i + 1);
          }
          i = ai < bi && ai >= 0 ? ai : bi;
        }
        if (begs.length) {
          result = [left, right];
        }
      }
      return result;
    }