Update Array.from callback signature

It's up to latest TC39 consensus:
https://github.com/rwaldron/tc39-notes/blob/master/es6/2014-04/apr-9.md#conclusionresolution-4
Simplify isCallable

It seems in ES5+ world each callable object is typeof function
Add deprecated note
Remove isCallable from docs
Do not rely on isCallable in validCallable