setup.py: improvements

- Use README.md content for long_description;
- Add python_requires.

setup.py

@@ -6,17 +6,21 @@
 
 
 HERE = pathlib.Path(__file__).resolve().parent
-with open(HERE / "src/caterpillar/version.py", encoding="utf-8") as fp:
+with HERE.joinpath("src/caterpillar/version.py").open(encoding="utf-8") as fp:
  exec(fp.read())
+with HERE.joinpath("README.md").open(encoding="utf-8") as fp:
+ long_description = fp.read()
 
 setuptools.setup(
  name="caterpillar-hls",
  version=__version__,
  description="Hardened HLS merger",
- long_description="See https://github.com/zmwangx/caterpillar#readme.",
+ long_description=long_description,
+ long_description_content_type="text/markdown",
  url="https://github.com/zmwangx/caterpillar",
  author="Zhiming Wang",
  author_email="[email protected]",
+ python_requires=">=3.6",
  license="MIT",
  classifiers=[
  "Development Status :: 5 - Production/Stable",