Update travis: use iOS 11.4

Author: e-marchand

.travis.yml

@@ -7,10 +7,10 @@ env:
     - PROJECT=Prephirences.xcodeproj
     - IOS_FRAMEWORK_SCHEME="PrephirencesiOS"
     - MACOS_FRAMEWORK_SCHEME="PrephirencesMac"
-    - IOS_SDK=iphonesimulator11.0
+    - IOS_SDK=iphonesimulator11.4
     - MACOS_SDK=macosx10.13
   matrix:
-    - DESTINATION="OS=11.0,name=iPhone 8" SCHEME="$IOS_FRAMEWORK_SCHEME" SDK="$IOS_SDK" RUN_TESTS="YES"
+    - DESTINATION="OS=11.4,name=iPhone 8" SCHEME="$IOS_FRAMEWORK_SCHEME" SDK="$IOS_SDK" RUN_TESTS="YES"
     - DESTINATION="arch=x86_64" SCHEME="$MACOS_FRAMEWORK_SCHEME" SDK=macosx10.13 RUN_TESTS="YES"
 before_install:
   - gem install xcpretty --no-rdoc --no-ri --no-document --quiet