Attempt to add tests to github actions

.github/workflows/tests.yml

@@ -0,0 +1,24 @@
+name: Tests
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - name: Download submodules
+        run: |
+          git submodule update --init --recursive
+          git submodule sync -q
+          git submodule update --init
+      - name: Set up Python
+        uses: actions/setup-python@v1
+        with:
+          python-version: [2.7, 3.4, 3.5, 3.6, 3.7, 3.8]
+      - name: Install dependencies
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r nearley-requirements.txt
+      - name: Run tests
+        run: |
+          python -m tests