Update .travis.yml

Author: swiftlyfalling

.travis.yml

@@ -23,7 +23,7 @@ git:
 #  - DESTINATION="generic/platform=iOS"
 #  - DESTINATION="generic/platform=watchOS"
 #  - DESTINATION="generic/platform=tvOS"
-#  - DESTINATION="platform=iOS Simulator,name=iPhone 6s,OS=10.3"
+#  - DESTINATION="platform=iOS Simulator,name=iPhone 6s,OS=10.3.1"
 
 matrix:
   include:
@@ -84,7 +84,7 @@ matrix:
       osx_image: xcode8.3
       gemfile: .ci/Gemfile.travis
       env:
-        - DESTINATION="platform=iOS Simulator,name=iPhone 6s,OS=10.3"
+        - DESTINATION="platform=iOS Simulator,name=iPhone 6s,OS=10.3.1"
 
 script:
   - cd .ci