add a configure about ess-smart-S-assign

[Vonfry]

If one don't want to use ess-smart-S-assign-key, he must use some toggle function. But this is not explicit. For example, if some one write it twice in init file, it will start again.

Would you like to add some function like (ess-smart-S-assign-mode nil) to disable it indeed.

Or let we set ess-smart-S-assign-key to nil. I try to this but it will throw a exception when require this package.

[jabranham]

I've had a few people ask me how to disable this, so you're not the only one who finds this annoying, especially that you can't set ess-smart-S-assign-key to nil. I'm not a huge fan of it personally and I've just been doing (defalias 'ess-smart-S-assign #'self-insert-command) in my init.el to get rid of this.

#559 makes it possible to disable this by setting ess-smart-S-assign-key to nil.

[vspinu]

One can simply do (define-key ess-mode-map [?_] nil) and be done with it.

The goggling should never been there in the first place. It mostly confuses users.

[jabranham]

Well, you'd have to do that to inferior-ess-mode-map as well, which isn't terribly complicated I agree.

The PR I mentioned allows users to set ess-smart-S-assign to nil. I've had at least four or five people ask me why that's not possible. It came up on #emacs on IRC just last week.

Plus it gets rid of ~80 lines of code :-)