setup.py: use setuptools

As per [1] distutils is now deprecated in Python 3.10, and will be
entirely removed in Python 3.12.

Setuptools has an almost identical API, so simply switch to that.

[1] https://docs.python.org/3/whatsnew/3.10.html#distutils-deprecated

Closes #52

setup.py

@@ -9,14 +9,13 @@
 #-
 
 import sys
-import distutils.core
+import setuptools
 
 if sys.version_info < (3, 5):
     sys.stderr.write("This module requires Python 3.5 or later.\n")
     sys.exit(-1)
 
-distutils.core.setup \
-  (
+setuptools.setup(
     name = "DBussy",
     version = "1.3",
     description = "language bindings for libdbus, for Python 3.5 or later",
@@ -27,4 +26,4 @@
     license = "LGPL v2.1+",
     python_requires='>=3.5',
     py_modules = ["dbussy", "ravel"],
-  )
+)