Update .travis.yml (#114)

Expanded the Travis CI testing matrix to include older iOS versions.

.travis.yml

@@ -1,11 +1,31 @@
 language: objective-c
-osx_image: xcode8.3
+osx_image: xcode9.2
 sudo: false
+env:
+  global:
+  - LC_CTYPE=en_US.UTF-8
+  - LANG=en_US.UTF-8
+  - LANGUAGE=en_US.UTF-8
+matrix:
+  include:
+    - osx_image: xcode9.2
+      env: COVERAGE=code_coverage SDK="iphonesimulator11.2" DESTINATION="name=iPhone 6s,OS=11.2"
+    - osx_image: xcode9.2
+      env: SDK="iphonesimulator11.2" DESTINATION="name=iPhone 6s,OS=10.3.1"
+    - osx_image: xcode9.2
+      env: SDK="iphonesimulator11.2" DESTINATION="name=iPhone 6s,OS=9.3"
+    - osx_image: xcode9.2
+      env: SDK="iphonesimulator11.2" DESTINATION="name=iPhone 6,OS=8.4"
+    - osx_image: xcode8.3
+      env: SDK="iphonesimulator10.3" DESTINATION="name=iPhone 6,OS=8.1"
 before_install:
   - gem install cocoapods --no-rdoc --no-ri --no-document --quiet
   - pod install --repo-update
 script:
   - set -o pipefail
-  - xcodebuild test -workspace MotionAnimator.xcworkspace -scheme MotionAnimatorCatalog -sdk "iphonesimulator10.3" -destination "name=iPhone 6s,OS=10.3.1" -enableCodeCoverage YES ONLY_ACTIVE_ARCH=YES | xcpretty -c;
+  - xcodebuild test -workspace MotionAnimator.xcworkspace -scheme MotionAnimatorCatalog -sdk "$SDK" -destination "$DESTINATION" -enableCodeCoverage YES ONLY_ACTIVE_ARCH=YES | xcpretty -c;
 after_success:
+  - if [ "$COVERAGE" == "code_coverage" ]; then
+     bash <(curl -s https://codecov.io/bash);
+    fi
   - bash <(curl -s https://codecov.io/bash)