The readme.txt itself needs to be updated.
For example, you haven’t mentioned the plugin works with WordPress 4.x (other than at the top “Tested up to: 4.0”); I’ve used it successfully with probably every minor update through the current WordPress version 4.2.2, on Apache and IIS7 servers.
The ottopress.com instructions are good for configuring CNAME/ANAME but are not updated for WordPress changes over the last 5 years.
My instructions cover how to put site IDs into the plugin settings pages, and what the Domain and Path settings should be, plus all the other settings needed. https://lcblog.lernerconsult.com/2012-wordpress-3-multi-site-domain-mapping/