Merge pull request #13 from jasnow/master

Added [2.2.5, 2.3.1, 'cache: bundler'] to .travis.yml file

Author: e2

.travis.yml

@@ -5,5 +5,8 @@ rvm:
   - 2.0.0
   - 2.1.9
   - 2.2.4
+  - 2.2.5
+  - 2.3.1
   - jruby-9.0.5.0
 before_install: gem install bundler -v 1.12.1
+cache: bundler