Update travis configuration for xcode8 and swift3 build

.travis.yml

@@ -1,8 +1,18 @@
 language: objective-c
+osx_image: xcode8
+env:
+  global:
+  - LC_CTYPE=en_US.UTF-8
+  - LANG=en_US.UTF-8
+  - WORKSPACE=AccountBalance.xcworkspace
+  - SCHEME=AccountBalance
+  - SDK=macosx10.12
+  - DESTINATION="arch=x86_64"
 cache:
   - bundler
   - cocoapods
-osx_image: xcode7.3
-xcode_workspace: AccountBalance.xcworkspace
-xcode_scheme: AccountBalance
-xcode_sdk: macosx10.11
+before_install:
+  - gem install cocoapods --pre --no-rdoc --no-ri --no-document --quiet
+  - pod update
+script: 
+  - xcodebuild -workspace "$WORKSPACE" -scheme "$SCHEME" -sdk "$SDK" -destination "$DESTINATION" -configuration Release ONLY_ACTIVE_ARCH=NO build | xcpretty