add test for 3.9

Author: satra

.github/workflows/pythonpackage.yml

@@ -16,7 +16,7 @@ jobs:
     strategy:
       matrix:
         os: [macos-latest, ubuntu-18.04]
-        python-version: [3.7, 3.8]
+        python-version: [3.7, 3.8, 3.9]
 
     steps:
     - uses: actions/checkout@v2

setup.cfg

@@ -18,6 +18,8 @@ classifiers =
     Operating System :: MacOS :: MacOS X
     Operating System :: POSIX :: Linux
     Programming Language :: Python :: 3.7
+    Programming Language :: Python :: 3.8
+    Programming Language :: Python :: 3.9
     Topic :: Scientific/Engineering
 
 [options]