Upate CI to split out different python versions by container

.github/workflows/ci.yml

@@ -3,21 +3,16 @@ on: [pull_request]
 jobs:
   Test:
     runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: [3.6, 3.7, 3.8]
     steps:
     - uses: actions/checkout@v2
-    - name: Set up Python 3.6
+    - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v1
       with:
-        python-version: 3.6
-    - name: Set up Python 3.7
-      uses: actions/setup-python@v1
-      with:
-        python-version: 3.7
-    - name: Set up Python 3.8
-      uses: actions/setup-python@v1
-      with:
-        python-version: 3.8
+        python-version: ${{ matrix.python-version }}
     - name: Run tox automation
       run: |
-        pip install tox
+        pip install tox==3.14.5
         tox