static script(content, options = {}) {
    options = new Options(options);  // fresh copy, don't write on argument.
    options.script = true;
    return new Compiler(options).compile(content);
  }
Use Traceur to compile ES6 type=script source code to ES5 script.

@param  {string} content ES6 source code.
@param  {Object=} options Traceur options to override defaults.
@return {Promise<{js: string, errors: Array, sourceMap: string}>} Transpiled code.