Add code-review devref for release notes
Add code-review devref for release notes

Now that we use reno, we need to provide some docs for explaining when
to provide a reno file.

Change-Id: Iebdbdad11986726aeebbf8fdc27e8dbe0bffb299

alaski/nova,BeyondTheClouds/nova,Juniper/nova,jianghuaw/nova,jianghuaw/nova,openstack/nova,BeyondTheClouds/nova,phenoxim/nova,rajalokan/nova,vmturbo/nova,Juniper/nova,cernops/nova,bigswitch/nova,zhimin711/nova,apporc/nova,rajalokan/nova,cloudbase/nova,cloudbase/nova,cernops/nova,rahulunair/nova,dims/nova,jianghuaw/nova,zhimin711/nova,Juniper/nova,mikalstill/nova,devendermishrajio/nova,sebrandon1/nova,klmitch/nova,gooddata/openstack-nova,sebrandon1/nova,rahulunair/nova,devendermishrajio/nova,hanlind/nova,rajalokan/nova,cernops/nova,NeCTAR-RC/nova,Juniper/nova,cloudbase/nova,jianghuaw/nova,mikalstill/nova,vmturbo/nova,NeCTAR-RC/nova,bigswitch/nova,vmturbo/nova,alaski/nova,mahak/nova,CEG-FYP-OpenStack/scheduler,klmitch/nova,gooddata/openstack-nova,klmitch/nova,openstack/nova,CEG-FYP-OpenStack/scheduler,mahak/nova,vmturbo/nova,cyx1231st/nova,klmitch/nova,gooddata/openstack-nova,dims/nova,BeyondTheClouds/nova,sebrandon1/nova,mahak/nova,phenoxim/nova,cyx1231st/nova,gooddata/openstack-nova,hanlind/nova,apporc/nova,openstack/nova,rahulunair/nova,rajalokan/nova,mikalstill/nova,hanlind/nova