Ok, I really thought that this is a good idea. But, now it seems to me that I was wrong.

Why?

1. First of all, it is very limited. For example, you cannot write def a(instance: Union[str, bytes]). We can only work with Instance types because of the limited runtime-dispatch capabilities
2. It makes our code much more complex. And I mean it! With this feature we now have to typecheck a whole other set of cases. Let's see some examples:

def ex():
   ...

some.instance(ex)  # will typecheck, because we allow callables, but should not.
# So, we need a plugin support for this - and it is really complex, because it has lots of corner cases

3. It makes our code much less type-safe. There are cases when Callable should not be allowed into first .instance() call
4. Runtime algorithm is not perfect as well, it is now focused on getattr(arg, '__annotations__') and the thing is arg might have __annotations__ even if it is not a function. So, I need to figure out another solution. But, probably the best way to solve this is to remove this feature

So, I have decided to remove this. Yes, it is a breaking changed, but there are just several users, and upgrade is really easy.

Reverts #136