update bundler on travis as old version does not play nice with newer rubygems

Author: mpapis

.travis.yml

@@ -6,6 +6,7 @@ before_install:
   - rvm default do gem install execjs
   - git config --global user.name "Pre Commit"
   - git config --global user.email "[email protected]"
+  - gem update bundler
 cache:
  - bundler
  - npm