Added iOS 8-11 test matrix for Travis

Author: dingwilson

.travis.yml

@@ -1,3 +1,13 @@
-osx_image: xcode8.0
+osx_image: xcode9.2
 language: objective-c
-xcode_project: GroupWork.xcodeproj
+xcode_project: GroupWork.xcodeproj
+
+env:
+  - UDID="7A5E86EB-E32C-475F-8FF5-10AA330C1D34", IOS_DEVICE="iPhone 7 Plus (11.1)"
+  - UDID="15E2107D-EAD2-4E1F-8BC3-59E58E750FB1", IOS_DEVICE="iPhone 7 (10.0)"
+  - UDID="9AB3D590-C748-4E17-8E35-67B298E973F7", IOS_DEVICE="iPhone 6 Plus (9.0)"
+  - UDID="80BE80F4-C243-43F0-BD95-5CB085DAD04F", IOS_DEVICE="iPhone 6 (8.1)"
+
+script:
+  - open -a "simulator" --args -CurrentDeviceUDID $UDID
+  - xcodebuild clean test -project GroupWork.xcodeproj -scheme GroupWork -configuration Debug -sdk iphonesimulator -destination "platform=iOS Simulator,id=$UDID" CODE_SIGN_IDENTITY=\"\" CODE_SIGNING_REQUIRED=NO ONLY_ACTIVE_ARCH=NO -quiet