.travis.yml in ridgepole-0.7.4 vs .travis.yml in ridgepole-0.7.5.beta

@@ -4,13 +4,16 @@
 language: ruby
 cache:
   - bundler
   - apt
 rvm:
-  - 2.2.9
   - 2.3.6
-  - 2.4.3
-  - 2.5.0
+  - 2.4.5
+  - 2.5.3
+  - 2.6.0-preview2
+matrix:
+  allow_failures:
+    - rvm: 2.6.0-preview2
 before_script:
   - sudo service mysql stop
   - sudo service postgresql stop
   - docker-compose up -d
   - function mysql_ping { mysqladmin -u root -h 127.0.0.1 -P 13316 -ppassword ping; }