Upgrade travisci to xcode 9.2

Luc Dion · Luc Dion · commit 5882ebd298fa · 2017-12-19T16:30:23.000-05:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,5 +1,5 @@
 language: objective-c
-osx_image: xcode9
+osx_image: xcode9.2 
 
 env:
   matrix:
