Update README.md file according to README.md template on 2.x-dev

Patch has some issues:

12.diff:85: trailing whitespace.
   - A method to build a list of item IDs to warm.
warning: 1 line adds whitespace errors.

and also, Configuration is required section as per readme.md template and it is empty. Please review.

I don't know what #5 is about. I just clicked the button for merging, as usual...

Automatically closed - issue fixed for 2 weeks with no activity.