Update dependencies and add ci checks for python 3.9 (danielgtaylor#173)

* Update locked dependencies to fix grpcio compile issue with python 3.9
* ci: add python 3.9

Author: abn

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
     strategy:
       matrix:
         os: [Ubuntu, MacOS, Windows]
-        python-version: [3.6, 3.7, 3.8]
+        python-version: [3.6, 3.7, 3.8, 3.9]
         exclude:
           - os: Windows
             python-version: 3.6