Currently the Python 2 stub for `IntEnum` just inherits from `Enum` without changing anything, meaning that its `value` has type `Any`. This changes it such that, if you know you have an `IntEnum` you get the more specific `int` type for the `value`. Note that this has already been done for Python 3 `IntEnum` (both in `third_party/3/enum.pyi` and `stdlib/3.4/enum.pyi`).
I went through each method in the source and verified the inputs it accepts and outputs it gives. I also redefined a few methods on the `Path` class so that MyPy knows they return `Path` instead of `PurePath`. This is really just a temporary workaround until https://github.com/python/mypy/issues/1212 is fixed, but greatly improves the process of working with the `pathlib` module and is therefore likely worth the duplication.
