Remove funbox.passthrough.passnone, or at least move it into maybe

[nmbooker]

funbox.maybe.maybe_c(f)(val) is equivalent to funbox.passthrough.passnone(f)(val).

funbox.maybe is more general, in that it can take more functions, applying them left to right like in a pipeline. I think that the new interface of 'maybe' makes a chain of more than one or two much easier to read than nested calls to passnone.

maybe_c(f, g, h, ...)(val)

There's also an uncurried version, maybe(), which will be more convenient in the common case that you're not passing the chain of lifted functions as arguments to another higher-order function.

maybe(val, f, g, h, ...)

The only thing passnone()() can do that maybe_c()() or maybe() can't is to allow you to change the default return value for the None case:

>>> passnone(lambda x: x.upper(), default='NULL')(None)
'NULL'

That's the only thing that may make it worth keeping.

If I do keep passnone, I'll move it into maybe, but it may have a different name or interface.

If anyone currently uses passnone in this way, please comment below.