.travis.yml in tee_logger-3.1.1 vs .travis.yml in tee_logger-3.1.2

@@ -1,10 +1,9 @@
 language: ruby
+cache: bundler
 rvm:
-  - ruby-head
   - 2.2.3
-  - 2.2.2
-  - 2.1.5
+  - 2.1.7
   - 2.0.0
 before_install: gem install bundler -v 1.10.4
 notifications:
   slack:
     secure: 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