travis: use xcode8 as default image

Author: jberkel

.travis.yml

@@ -1,40 +1,40 @@
 language: objective-c
 rvm: 2.2
+osx_image: xcode8
 matrix:
   include:
-    - os: osx
-      osx_image: xcode8
-      env:
+    - env:
         - BUILD_SCHEME="SQLite iOS"
         - IOS_SIMULATOR="iPhone SE"
-    - os: osx
-      osx_image: xcode8
-      env: BUILD_SCHEME="SQLite Mac"
-    - os: osx
-      osx_image: xcode8
-      env:
+    - env: BUILD_SCHEME="SQLite Mac"
+    - env:
         - VALIDATOR_SUBSPEC="none"
         - IOS_SIMULATOR="iPhone SE"
-    - os: osx
-      osx_image: xcode8
-      env:
+    - env:
         - VALIDATOR_SUBSPEC="standard"
         - IOS_SIMULATOR="iPhone SE"
-    - os: osx
-      osx_image: xcode8
-      env:
+    - env:
         - VALIDATOR_SUBSPEC="standalone"
         - IOS_SIMULATOR="iPhone SE"
-    - env: BUILD_SCHEME="SQLite iOS"
-    - env: BUILD_SCHEME="SQLite Mac"
-    - env: VALIDATOR_SUBSPEC="none"
-    - env: VALIDATOR_SUBSPEC="standard"
-    - env: VALIDATOR_SUBSPEC="standalone"
+    - os: osx
+      osx_image: xcode7.3
+      env: BUILD_SCHEME="SQLite iOS"
+    - os: osx
+      osx_image: xcode7.3
+      env: BUILD_SCHEME="SQLite Mac"
+    - os: osx
+      osx_image: xcode7.3
+      env: VALIDATOR_SUBSPEC="none"
+    - os: osx
+      osx_image: xcode7.3
+      env: VALIDATOR_SUBSPEC="standard"
+    - os: osx
+      osx_image: xcode7.3
+      env: VALIDATOR_SUBSPEC="standalone"
 before_install:
   - gem install xcpretty --no-document
 script:
   - ./run-tests.sh
 after_failure:
   - find $HOME/Library/Developer/Xcode/DerivedData/ -name '*.log' -print0 | xargs -0 cat
   - cat /var/log/system.log
-osx_image: xcode7.3