Update Travis build server to use Xcode 7.2.

Scott Goodson · Scott Goodson · commit 89f9fc551f4c · 2015-12-25T15:59:46.000-08:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,5 +1,5 @@
 language: objective-c
-osx_image: xcode7
+osx_image: xcode7.2
 before_install:
   - brew update
   - brew reinstall xctool
