Fix travis config

.travis.yml

@@ -10,7 +10,7 @@ matrix:
       compiler: gcc
 
 before_install:
-  - if [ "$TRAVIS_OS_NAME" == "osx" ]; then rvm install 2.1 && rvm use 2.1 && ruby -v; fi
+  - if [ "$TRAVIS_OS_NAME" == "osx" ]; then rvm install 2.3 && rvm use 2.3 && ruby -v; fi
   - if [ "$TRAVIS_OS_NAME" == "linux" ]; then sudo apt-get install --assume-yes --quiet gcc-multilib; fi
 install:
   - gem install rspec