Fix module entry point declaration
Fix module entry point declaration

Explicit definition of a py::module was only required when using the
deprecated PYBIND11_PLUGIN macro; remove this as the second argument of
the PYBIND11_MODULE macro will define the variable.

Set the docstring as appropriate.

Fixes #404.

lief-project/LIEF,lief-project/LIEF,lief-project/LIEF,lief-project/LIEF