Merge pull request #9 from ruby/ci-use-bundler-cache

CI: use bundler-cache, and 'bundle exec'

Author: hsbt

.github/workflows/test.yml

@@ -16,7 +16,6 @@ jobs:
       uses: ruby/setup-ruby@v1
       with:
         ruby-version: ${{ matrix.ruby }}
-    - name: Install dependencies
-      run: bundle install
+        bundler-cache: true # 'bundle install' and cache gems
     - name: Run test
-      run: rake test
+      run: bundle exec rake test