[Travis] Build matrix for Xcode 7.3 and Xcode 8

Author: ikesyo

.travis.yml

@@ -1,13 +1,19 @@
 language: objective-c
-osx_image: xcode7.3
 xcode_workspace: ReactiveTask.xcworkspace
-xcode_scheme: ReactiveTask
 git:
   submodules: false
 before_script:
   - git submodule update --init --recursive
 script:
   - set -o pipefail && xcodebuild -workspace "$TRAVIS_XCODE_WORKSPACE" -scheme "$TRAVIS_XCODE_SCHEME" test | xcpretty
+matrix:
+  include:
+    - osx_image: xcode7.3
+      xcode_scheme: ReactiveTask
+      env: JOB=Xcode7.3
+    - osx_image: xcode8
+      xcode_scheme: ReactiveTask
+      env: JOB=Xcode8
 notifications:
   email: false
   slack:
@@ -27,3 +33,4 @@ deploy:
   on:
     repo: Carthage/ReactiveTask
     tags: true
+    condition: $JOB = Xcode7.3