use Xcode8.3 OS X image

Author: Vladimir Kotal

.travis.yml

@@ -9,7 +9,7 @@ matrix:
       sudo: required
       jdk: oraclejdk8
     - os: osx
-      osx_image: xcode7.3
+      osx_image: xcode8.3
 before_install: scripts/before_install
 install: true
 before_script: scripts/before