.travis.yml in simctl-1.6.2 vs .travis.yml in simctl-1.6.3

@@ -1,20 +1,21 @@
 language: objective-c
 matrix:
   include:
     - os: osx
-      osx_image: xcode7.3
+      osx_image: xcode8.3
       env: CUSTOM_DEVICE_SET_PATH=true
     - os: osx
-      osx_image: xcode7.3
+      osx_image: xcode8.3
       env: CUSTOM_DEVICE_SET_PATH=false
     - os: osx
-      osx_image: xcode8.2
+      osx_image: xcode9
       env: CUSTOM_DEVICE_SET_PATH=true
     - os: osx
-      osx_image: xcode8.2
+      osx_image: xcode9
       env: CUSTOM_DEVICE_SET_PATH=false
 before_script:
   - export LANG=en_US.UTF-8
 install: bundle
 script:
   - bundle exec rake
+  - bundle exec rubocop