Update travis to use iPhone 8

Author: ps2

.travis.yml

@@ -17,5 +17,5 @@ script:
     - set -o pipefail && xcodebuild -project Loop.xcodeproj -scheme Loop build CODE_SIGN_IDENTITY="" CODE_SIGNING_ALLOWED=NO | xcpretty
     - set -o pipefail && xcodebuild -project Loop.xcodeproj -scheme Learn build CODE_SIGN_IDENTITY="" CODE_SIGNING_ALLOWED=NO | xcpretty
     # Run the test target
-    - set -o pipefail && xcodebuild -project Loop.xcodeproj -scheme LoopTests -destination 'name=iPhone 6' test | xcpretty
-    - set -o pipefail && xcodebuild -project Loop.xcodeproj -scheme DoseMathTests -destination 'name=iPhone 6' test | xcpretty
+    - set -o pipefail && xcodebuild -project Loop.xcodeproj -scheme LoopTests -destination 'name=iPhone 8' test | xcpretty
+    - set -o pipefail && xcodebuild -project Loop.xcodeproj -scheme DoseMathTests -destination 'name=iPhone 8' test | xcpretty