options: support options in urls via `pagespeed AddOptionsToUrls`

* Support AddOptionsToUrls
* Support tests that need top run something post cache flush
* Add `ps_determine_port` so we parse urls out of ports and fix #239
* Rejigger the tests to support how our headers for resources don't include a
  Content-Length header
Merge pull request #240 from pagespeed/jefftk-config-in-url

Support `pagespeed AddOptionsToUrls`