Mention in the readme that overriding user's foldtext is a configurable option

[dyloxim]

I was frustrated to see that this plugin set the foldtext on behalf of the user (not expected since the readme says this plugin only consists of fold expressions) but after a quick look at the source was pleased to see that an option exists to disable this functionality - it would probably save some confusion for others if this behaviour, and the option itself was mentioned in the readme.

the option is:
let g:markdown_fold_override_foldtext=0