loadMode is no longer emitted

[gjtorikian]

We're indicating that loadMode is emitted in the docs: https://github.com/ajaxorg/ace/blob/master/lib/ace/edit_session.js#L99-L104

But I think this was taken out in the recent highlighting refactor.

Either we emit it again, or remove the comment.

[nightwing]

Now there is only generic loadModule event emitted in config
Also we should add a note about this to changelog