Added PageKite

Hey! Cool list, I hope you will accept PageKite as an addition.

Here's a brief essay I wrote about the philosophy of the project which hopefully explains why I feel it belongs: https://pagekite.net/wiki/Floss/FreedomAndPrivacy/

Note that although there is a commercial entity providing relay service, the company serves the project, not the other way around. And the relay code is fully open source so people can run their own if they so choose.