ci: add 2.7 (#871)

KazuCocoa · web-flow · commit f1734ab0ff2a · 2019-12-27T07:03:21.000+09:00
diff --git a/.travis.yml b/.travis.yml
@@ -7,6 +7,7 @@ rvm:
   - 2.4
   - 2.5
   - 2.6
+  - 2.7
 
 install:
   - bundle install --retry=3
