How to permanently disable resume on El Capitan
There is a simple method for this, for anyone using Lion+.

Navigate to /username/Library

Cannot see Library Folder: While in Finder > Press and Hold OPT key Down > under GO Menu> Select Library

Once there, you will see a folder named Saved Application State

To disable ALL resume states, 


right-click on Saved Application State > Get info
select Locked checkbox


To disable SOME resume states


right-click on Saved Application State/Sub-Folder Name > Get info
select Locked checkbox






That's it.