.travis.yml in async-io-1.8.4 vs .travis.yml in async-io-1.8.5

@@ -1,9 +1,14 @@
 language: ruby
 sudo: false
 dist: trusty
 cache: bundler
 
+before_script: 
+  - gem update --system
+  - gem install bundler
+
+
 matrix:
   include:
     - rvm: 2.2
     - rvm: 2.3
     - rvm: 2.4