Use Xcode 7.3 and SDK 9.3 in Travis
diff --git a/.travis.yml b/.travis.yml
index a993b55..75b1440 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,5 @@
 language: objective-c
-osx_image: xcode7.2
+osx_image: xcode7.3
 env:
   global:
     - CONFIG=opt
@@ -27,6 +27,6 @@
   - InteropTestsLocalCleartext
   # TODO(jcanizales): Investigate why they time out:
   # - InteropTestsRemote
-xcode_sdk: iphonesimulator9.2
+xcode_sdk: iphonesimulator9.3
 notifications:
   email: false