update setup.py description & add Python 3.9

setup.py

@@ -1,23 +1,24 @@
 from setuptools import setup
 
-with open("README.md", "r") as fh:
+with open('README.md', 'r') as fh:
     long_description = fh.read()
 
 setup(
     name='FlowIO',
     version='0.9.12b',
     packages=['flowio'],
     package_data={'': []},
-    description='Flow Cytometry Standard I/O',
+    description='FlowIO is a Python library for reading / writing Flow Cytometry Standard (FCS) files',
     long_description=long_description,
-    long_description_content_type="text/markdown",
-    author="Scott White",
-    author_email="[email protected]",
+    long_description_content_type='text/markdown',
+    author='Scott White',
+    author_email='[email protected]',
     license='BSD',
-    url="https://github.com/whitews/flowio",
+    url='https://github.com/whitews/flowio',
     requires=[],
-    data_files=[("", ["LICENSE"])],
+    data_files=[('', ['LICENSE'])],
     classifiers=[
+        'Programming Language :: Python :: 3.9',
         'Programming Language :: Python :: 3.8',
         'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: 3.6'