These macros now support specifying an argument list:
`py_fn!(myfn(myarg: i32))`
will expect `myfn` to be a function with the signature:
`fn myfn<'p>(py: Python<'p>, myarg: i32) -> PyResult<'p, _>`
It can called from python as `myfn(1)`
or using keyword arguments: `myfn(myarg=1)`.
If no parameter list is specified (`py_fn!(myfn)`), the expected signature
now includes the keyword arguments:
`fn run<'p>(py: Python<'p>, args: &PyTuple<'p>, kwargs: Option<&PyDict<'p>>)`
Due to the additional `kwargs` argument, this is a [breaking-change].
Daniel Grunwald