Force removal of bundler before installing a new version

Author: rastating

.travis.yml

@@ -7,7 +7,8 @@ rvm:
   - 2.2.4
   - 2.3.0
 before_install:
-  - "gem install bundler 1.13.7"
+  - "gem uninstall bundler"
+  - "gem install bundler -v 1.13.7"
   - "echo 'gem: --no-ri --no-rdoc' > ~/.gemrc"
 script: bundle exec rspec
 branches: