Minor improvements to setup.py

setup.py

@@ -1,3 +1,5 @@
+from pathlib import Path
+
 from setuptools import setup, find_packages
 
 from async_generator import __version__
@@ -6,15 +8,14 @@
     name="async_generator",
     version=__version__,
     description="Async generators for Python 3.5",
-    long_description=open("README.rst").read(),
+    long_description=Path(__file__).with_name("README.rst").read_text('utf-8'),
     author="Nathaniel J. Smith",
     author_email="njs@pobox.com",
     license="MIT",
     packages=find_packages(),
     url="https://github.com/njsmith/async_generator",
-    py_modules=["async_generator"],
     classifiers=[
-        "Development Status :: 4 - Beta",
+        'Development Status :: 5 - Production/Stable',
         "Intended Audience :: Developers",
         "License :: OSI Approved :: MIT License",
         "Programming Language :: Python :: 3",