Bump default to 2.7 (#19)

.github/workflows/ruby.yml

@@ -7,10 +7,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v1
-    - name: Set up Ruby 2.6
+    - name: Set up Ruby 2.7
       uses: actions/setup-ruby@v1
       with:
-        ruby-version: 2.6.x
+        ruby-version: 2.7.x
     - name: Build and test with Rake
       run: |
         gem install bundler
@@ -39,10 +39,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v1
-    - name: Set up Ruby 2.6
+    - name: Set up Ruby 2.7
       uses: actions/setup-ruby@v1
       with:
-        ruby-version: 2.6.x
+        ruby-version: 2.7.x
     - name: Test gem in Rails application
       run: |
         cd spec/rails