Do testing at GitHub Actions

.github/workflows/main.yml

@@ -1,9 +1,38 @@
-name: CI on Windows
+name: CI
 
 on: [push, pull_request]
 
 jobs:
-  build:
+  ubuntu:
+    runs-on: ubuntu-16.04
+    strategy:
+      fail-fast: false
+      matrix:
+        name: [py36, py37]
+        include:
+        - name: py36
+          python: 3.6
+          docutils: du13
+        - name: py37
+          python: 3.7
+          docutils: du14
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python ${{ matrix.python }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python }}
+    - name: Check Python version
+      run: python --version
+    - name: Install graphviz
+      run: sudo apt-get install graphviz
+    - name: Install dependencies
+      run: pip install -U tox
+    - name: Run Tox
+      run: tox -e ${{ matrix.docutils }} -- -vv
+
+  windows:
     runs-on: windows-latest
     strategy:
       matrix:

.travis.yml

@@ -14,12 +14,6 @@ jobs:
     - python: '3.5'
       env:
         - TOXENV=du12
-    - python: '3.6'
-      env:
-        - TOXENV=du13
-    - python: '3.7'
-      env:
-        - TOXENV=du14
     - python: '3.8'
       env:
         - TOXENV=du15