Add Github Actions workflow to run tox

.github/workflows/run-tox.yml

@@ -0,0 +1,25 @@
+name: Run Tox
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python: [2.7, 3.6, 3.7, 3.8, 3.9]
+
+    steps:
+      - uses: actions/checkout@v2
+      - name: Setup Python
+        uses: actions/setup-python@v2
+        with:
+          python-version: ${{ matrix.python }}
+      - name: Install Tox
+        run: pip install tox
+      - name: Run Tox
+        run: tox -e py