function run(code, url, options) {
  var scriptEl = document.createElement('script');
  scriptEl.text = transformCode(code, url, options);
  headEl.appendChild(scriptEl);
}
Appends a script element at the end of the <head> with the content of code,
after transforming it.

@param {string} code The original source code
@param {string?} url Where the code came from. null if inline
@param {object?} options Options to pass to jstransform
@internal