Use Xcode 11.1 in Travis for Swift 4.2 and 5 support

kylefleming · kylefleming · commit e26709254657 · 2019-11-06T14:44:50.000+09:00
diff --git a/.travis.yml b/.travis.yml
@@ -1,4 +1,4 @@
-osx_image: xcode9.3
+osx_image: xcode11.1
 language: objective-c
 cache:
 - cocoapods
