bunlder 1 doesn't support ruby < 2.3

amatsuda · amatsuda · commit 2405c994e33a · 2019-05-20T19:31:11.000+09:00
diff --git a/.travis.yml b/.travis.yml
@@ -5,7 +5,7 @@ cache:
   bundler: true
 
 before_install:
-  - gem install bundler
+  - gem install bundler -v '< 2'
 
 rvm:
   - 1.9.3
