Update setup.py (#2481)

Author: seanpmorgan

setup.py

@@ -118,6 +118,7 @@ def has_ext_modules(self):
         "Programming Language :: Python :: 3.6",
         "Programming Language :: Python :: 3.7",
         "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.9",
         "Topic :: Scientific/Engineering :: Mathematics",
         "Topic :: Software Development :: Libraries :: Python Modules",
         "Topic :: Software Development :: Libraries",