Update TravisCI script

Author: alejandro-isaza

Diff for: .travis.yml

@@ -1,5 +1,11 @@
 language: objective-c
-xcode_project: C4iOS.xcodeproj
-xcode_scheme: C4
-osx_image: xcode8
-xcode_sdk: iphonesimulator
+osx_image: xcode8.1
+
+script:
+  - set -o pipefail && xcodebuild test -project C4iOS.xcodeproj -scheme C4 -destination 'platform=iOS Simulator,name=iPhone 6' | xcpretty
+  - pod lib lint
+
+before_install:
+  - brew update
+  - brew install swiftlint
+  - gem install cocoapods --pre --no-rdoc --no-ri --no-document --quiet