v2.0.0-rc.0 Faster CORS

[damienwebdev]

@fooman @indykoning @quangdo-aligent @aligent-lturner There's a very large performance improvement in v2.0.0. Please trial this if you're able to and let me know if there are any problems. I've released as v2.0.0-rc.0 as it is possibly breaking, and I'd like to deliver this pre-release in order to mitigate any broken code.

The important diff is here: #66

This should improve performance significantly.

With:

composer dump-autoload -o
bin/magento deploy:mode:set production
opcache.enabled=1

I was getting responses ~20ms (on-device so latency was negligible). Please let me know if you're seeing anything different.