Don't update rubygem/bundler

Author: n-rodriguez

.travis.yml

@@ -18,8 +18,6 @@ services:
 addons:
   postgresql: '9.6'
 before_install:
-  - gem update --system
-  # - gem install bundler --no-document
   - sh -c "if [ '$DB_ADAPTER' = 'mysql2' ]; then mysql -e 'create database ajax_datatables_rails;'; fi"
   - sh -c "if [ '$DB_ADAPTER' = 'postgresql' ]; then psql -c 'create database ajax_datatables_rails;' -U postgres; fi"
   - sh -c "if [ '$DB_ADAPTER' = 'oracle_enhanced' ]; then ./spec/install_oracle.sh; fi"