Broken links in documentation

There are twoo links pointing to `pobox.com`, which no longer hosts the intended pages. Below are the links I found in the Internet Archive to where pobox.com was previously redirecting.

http://pobox.com/~hp/free-software-ui.html -> https://www.ometer.com/free-software-ui.html
http://pobox.com/~hp/features.html -> https://www.ometer.com/features.html

I can update the files if you want.