A string, which supports escaping " and '  "milky way" 'he\'s the one!'
function (forceEscaped) {
                    var str, index = parserInput.i, isEscaped = false;

                    parserInput.save();
                    if (parserInput.$char('~')) {
                        isEscaped = true;
                    } else if (forceEscaped) {
                        parserInput.restore();
                        return;
                    }

                    str = parserInput.$quoted();
                    if (!str) {
                        parserInput.restore();
                        return;
                    }
                    parserInput.forget();

                    return new(tree.Quoted)(str.charAt(0), str.substr(1, str.length - 2), isEscaped, index, fileInfo);
                }