add CNAME for chicago.pm.org
Revert "add CNAME for chicago.pm.org" because github will redirect

This reverts commit 85af56a761309d13533030e451bc69e340481b63.
Add the CNAME back!

Revert "Revert "add CNAME for chicago.pm.org" because github will redirect"

This reverts commit ad4c5664be4d9e8e5e6f2926acba6b56d9836ff1.