Enable caching

This change enables caching during Travis builds

Author: nebhale

.travis.yml

@@ -4,6 +4,7 @@ rvm:
 - 1.9.3-p551
 before_script: if [[ $TRAVIS_RUBY_VERSION != '1.9.3-p551' || $TRAVIS_SECURE_ENV_VARS
   != 'true' ]]; then unset CODECLIMATE_REPO_TOKEN; fi
+cache: bundler
 notifications:
   slack:
     secure: TjtH21rnlUlNVu47g+cZSfgI+01RyAZzuMNU1nZskuUMJzf0PHGQAvA9VVVtC5SQiipGg0eB60xIlFN1VW/pYGw5yUcRkuqp9BUywC6CQFpduOc8fyBJ/ZD90Uu3tS/dCc5WCPRA1KPvGgtd6biofBuC/PJ8rMHQO6SVHUxGVvI=