CI: new Github Actions pipeline

.github/workflows/ci.yml

@@ -0,0 +1,55 @@
+name: Continuous integration
+
+on: 
+  push:
+  pull_request:
+
+jobs:
+  build:
+
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        python-version: [3.6, 3.7, 3.8, 3.9]
+
+    steps:
+    - uses: actions/checkout@v2
+
+    - name: Set up Python ${{ matrix.python-version }} on ${{ matrix.os }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python-version }}
+
+  - uses: actions/cache@v2
+    if: startsWith(runner.os, 'Linux')
+    with:
+      path: ~/.cache/pip
+      key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
+
+  - uses: actions/cache@v2
+    if: startsWith(runner.os, 'macOS')
+    with:
+      path: ~/Library/Caches/pip
+      key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
+
+  - uses: actions/cache@v2
+    if: startsWith(runner.os, 'Windows')
+    with:
+      path: ~\AppData\Local\pip\Cache
+      key: ${{ runner.os }}-pip-${{ hashFiles('**/requirements.txt') }}
+
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install -r requirements.txt
+
+    # Note the use of the -Wa flag to show DeprecationWarnings
+    - name: Unit tests
+      run: |
+        python -Wa -m unittest discover --verbose
+    
+    - name: Build documentation
+      run: |
+        pip install -r dev-requivements.txt
+        python setup.py build_sphinx