add github actions as CI

.github/worflows/ci.yml

@@ -0,0 +1,26 @@
+name: install & test
+
+on: [push, pull_request]
+
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+    name: python ${{ matrix.python-version }}
+
+    strategy:
+      matrix:
+        python-version: ["3.7", "3.8", "3.9"]
+
+    steps:
+    - uses: actions/checkout@v2
+    - uses: actions/setup-python@v2
+      with:
+            python-version: ${{ matrix.python-version }}
+
+    - name: install
+      shell: bash
+      run: pip install -e .
+
+    - name: test
+      shell: bash
+      run: python tests/test.py