Merge pull request #161 from kishikawakatsumi/travis_retry

Use travis_retry to rescue random ci failure

.travis.yml

@@ -8,7 +8,7 @@ before_script:
 - ./Lib/Scripts/decode_cert.sh || true
 - ./Lib/Scripts/add_key.sh || true
 script:
-- '(cd Lib && bundle exec rake $ACTION)'
+- '(cd Lib && travis_retry bundle exec rake $ACTION)'
 branches:
   only:
   - master