Use bundler 1.12.5 on travis

closes #7084

.travis.yml

@@ -23,7 +23,7 @@ branches:
     - 'develop'
 
 before_install:
-  - gem install bundler
+  - gem install bundler --version 1.12.5
   - mkdir travis-phantomjs
   - wget http://cifiles.diasporafoundation.org/phantomjs-2.1.1-linux-x86_64.tar.bz2 -O $PWD/travis-phantomjs/phantomjs-2.1.1-linux-x86_64.tar.bz2
   - tar -xvf $PWD/travis-phantomjs/phantomjs-2.1.1-linux-x86_64.tar.bz2 -C $PWD/travis-phantomjs

script/ci/build.sh

@@ -8,6 +8,6 @@ if [ "$DB" = "mysql" ]; then
   sed -i 's/*common/*mysql/' config/database.yml
 fi
 
-command="bundle exec rake --trace ci:travis:${BUILD_TYPE}"
+command="bundle _1.12.5_ exec rake --trace ci:travis:${BUILD_TYPE}"
 
 exec xvfb-run --auto-servernum --server-num=1 --server-args="-screen 0 1280x1024x8" $command