Only use lowercase and underscore for editor ID
Don't call settings_errors on options pages

Apparently it's called automatically there, according to an answer
(http://wordpress.stackexchange.com/a/18637/33110), so that's why
I've always had the double message issues. pass_settings_errors_id
should no longer be needed.
Update version and TOC
Tweak nonce name and CSS class
Update version to 1.1.8. Update documentation.