travis: Use newer xcode

tatsuhiro-t · tatsuhiro-t · commit a06d521aa7ef · 2018-01-04T21:11:03.000+09:00
diff --git a/.travis.yml b/.travis.yml
@@ -7,10 +7,7 @@ matrix:
     - os: linux
       compiler: clang
     - os: osx
-      osx_image: xcode7.3
-      compiler: clang
-    - os: osx
-      osx_image: xcode7
+      osx_image: xcode8.3
       compiler: clang
 sudo: false
 addons:
