Update pywb to 0.5.0

I've just released pywb 0.5.0 and wanted to update perma to use the latest.

The changes are pretty minor, most of the changes that you see are to the wombat.js which does client side rewriting. (Since its a static file, I added it manually to be part of the /static/ dir, however, it could also be served by pywb itself and avoid being in this repo).

Let me know if you have any questions.