CI: Move to github actions

.github/workflows/test.yml

@@ -0,0 +1,37 @@
+name: Test
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    name: on ruby ${{matrix.ruby}}
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        ruby: [2.3, 2.4, 2.5, 2.6, 2.7, '3.0', 3.1, head]
+        rails: ['rails42', 'rails50', 'rails51', 'rails52', 'rails60']
+        exclude:
+          - ruby: 2.3
+            rails: 'rails60'
+          - ruby: 2.4
+            rails: 'rails60'
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v2
+
+    - name: Set up Ruby
+      uses: ruby/setup-ruby@v1
+      with:
+        ruby-version: ${{matrix.ruby}}
+
+    - name: Install dependencies
+      run: bundle install --jobs 4 --retry 3
+
+    - name: Install appraisal dependencies
+      run: bundle exec appraisal ${{matrix.rails}} bundle install --jobs 4 --retry 3
+
+    - name: Specs
+      run: bundle exec appraisal ${{matrix.rails}} rake ci