.travis.yml in spreadsheet-1.1.8 vs .travis.yml in spreadsheet-1.1.9

@@ -1,9 +1,9 @@
 language: ruby
 sudo: false
 cache: bundler
 before_install:
-  - gem install bundler
+  - gem install bundler -v 1.17.3 --no-document
 bundler_args: --binstubs
 script: "bundle exec ruby test/suite.rb"
 rvm:
   - ruby-head
   - 2.3.3