code: function stringify(x) {
  	if (x === Object(x) && x.t === 'MetaString') return x.c;
  
    var result = [];
    var go = function (key, val) {
      if (key === 'Str') result.push(val);
      else if (key === 'Code') result.push(val[1]);
      else if (key === 'Math') result.push(val[1]);
      else if (key === 'LineBreak') result.push(' ');
      else if (key === 'Space') result.push(' ');
    };
    walk(x, go, '', {});
    return result.join('');
  }
docs: Walks the tree x and returns concatenated string content, leaving out all
  formatting.
  @param  {Object} x The object to walk
  @return {String}   JSON string