Have travis use a newer image for the OSX build (#10034)

Suggested by travis support for stopping the randomly-halting-builds issue.

Author: weswigham

.travis.yml

@@ -7,19 +7,14 @@ node_js:
 
 sudo: false
 
-os:
-  - linux
-  - osx
-
 matrix:
   fast_finish: true
-  exclude:
-  - os: osx
-    node_js: '4'
+  include:
   - os: osx
-    node_js: '0.10'
+    node_js: stable
+    osx_image: xcode7.3
 
 branches:
   only:
   - master
-  - transforms
+  - transforms