code: function(){
  
                  var tokenStream = this._tokenStream,
                      ws = "";
  
                  while(tokenStream.match(Tokens.S)){
                      ws += tokenStream.token().value;
                  }
  
                  return ws;
              }
docs: In some cases, you can end up with two white space tokens in a
  row. Instead of making a change in every function that looks for
  white space, this function is used to match as much white space
  as necessary.
  @method _readWhitespace
  @return {String} The white space if found, empty string if not.
  @private