`None` can be used as the desired signature of `with_signature`. This indicated that the user does not want to create a new function but only wants to update the metadata. Fixes [20](https://github.com/smarie/python-makefun/issues/20).
1.1.2
Fixed `isgeneratorfunction` for old python versions, see [decorator63](https://github.com/micheles/decorator/pull/63).
Python<3.3-specific function body is now not loaded at all if not needed.
1.1.1
`inject_as_first_arg` was missing from `with_signature`, added it. Fixed [18](https://github.com/smarie/python-makefun/issues/18).
1.1.0
Now `create_function` and `with_signature` create the same kind of function than the handler. So if it is a generator, a generator-based coroutine, or an async coroutine, the generated function will adapt. Fixes [6](https://github.com/smarie/python-makefun/issues/6).
1.0.2
Now a string signature can be provided to `with_signature` without problem. Fixed [17](https://github.com/smarie/python-makefun/issues/17).