* FromPyObject for all conversions that don't need to borrow temporaries
* RefFromPyObject for extracting references out of temporaries
(currently only used for extracting `&str`)
`<str as ToPyObject>::ObjectType` now always is `PyString`
(previously the type differed between Python 2.7 and 3.x)
`PyStringData` allows zero-copy access to Python's underlying string
representation.
* Introduce py_argparse_parse_plist!() to allow a more flexible
param list syntax.
* py_fn!() syntax changed
* Remove py_method!() / py_class_method!() macros.
These are of limited use when building dynamic types,
and not useful for py_class!() static types.
Since the `Python` token no longer is a part of `PyObject`,
lots of methods now require the token as additional argument.
This [breaking-change] breaks everything!
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].
