Workaround for rubygems/bundler#5349

Author: jorritfolmer

.travis.yml

@@ -1,10 +1,10 @@
 ---
 sudo: false
 language: ruby
-cache: bundler
+cache: false
 rvm:
 - jruby-1.7.25
 script:
 - bundle exec rspec spec
 jdk: oraclejdk8
-before_install: []
+before_install: gem install bundler -v 1.13.7