Upgrade varnish

- Delete old varnish cookbook. Who's dumb enough to use 2.0.x now anyway?
- Refactor varnish_frontend to figure out its own settings based on kernel data in /proc rather than instance meta data since new instance sizes were added in the THREE FREAKIN YEARS since this was updated
- Tweaks/fixes to at least get varnish to run. Hacked out unnecessary stuff from older versions.