Use github instead of Travis, which stopped working.

.github/workflows/test.yml

@@ -0,0 +1,34 @@
+name: Tests and coverage
+
+on:
+  push:
+    branches:
+      - '**'
+    tags:
+      - '**'
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    timeout-minutes: 30
+    strategy:
+      fail-fast: false
+      max-parallel: 4
+      matrix:
+        python-version: [2.7, 3.5, 3.6, 3.7, 3.8, 3.9, "3.10", "3.11-dev"]
+
+    steps:
+    - name: Checkout Code
+      uses: actions/checkout@v2
+      with:
+        fetch-depth: 0
+
+    - name: Setup Python environment
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python-version }}
+
+    - name: Test core code with pytest
+      run: |
+        pip install coverage pytest
+        coverage run -m py.test tests