Replace Travis with Github Actions

.github/workflows/2019.yml

@@ -0,0 +1,18 @@
+name: AOC 2019 test suite
+on:
+  push:
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-python@v2
+        with:
+          python-version: 3.9
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r 2019/requirements.txt
+      - name: Run Pytest
+        run: pytest 2019