Fix Ruby version in test matrix

This Ruby version should be 2.2.4 in favor of 482cab3.

Author: tricknotes

.travis.yml

@@ -24,11 +24,11 @@ matrix:
       gemfile: gemfiles/Gemfile.rails-edge
     - rvm: 2.1
       gemfile: gemfiles/Gemfile.rails-edge
-    - rvm: 2.2.2
+    - rvm: 2.2.4
       gemfile: gemfiles/Gemfile.rails-3.0
-    - rvm: 2.2.2
+    - rvm: 2.2.4
       gemfile: gemfiles/Gemfile.rails-3.1
-    - rvm: 2.2.2
+    - rvm: 2.2.4
       gemfile: gemfiles/Gemfile.rails-3.2
     - rvm: 2.3.0
       gemfile: gemfiles/Gemfile.rails-3.0