When rigging a function, offer to wrap its function arguments

[moodymudskipper]

Now function arguments will be ignored :

I don't think there's a way to deal with this automatically, but if we wrap() FUN then we're good :

Maybe we can have an additional argument to provide function args, and also get rid of the obsolete message in that case.

[moodymudskipper]

With #40 we might be able to test if the argument is a function once it's evaluated, then we'd wrap it, it doesn't need to be optional and would be more satisfying.