Adds clean step.

Author: michalkonturek

.travis.yml

@@ -6,5 +6,5 @@ before_install:
 - gem install cocoapods -v 1.1.1
 - pod install --project-directory=Example
 script:
-- set -o pipefail && xcodebuild test -workspace Example/KeyboardController.xcworkspace -scheme KeyboardController-Example -sdk iphonesimulator -destination 'name=iPhone 6,OS=10.0' ONLY_ACTIVE_ARCH=NO | xcpretty
+- set -o pipefail && xcodebuild clean test -workspace Example/KeyboardController.xcworkspace -scheme KeyboardController-Example -sdk iphonesimulator -destination 'name=iPhone 6,OS=10.0' ONLY_ACTIVE_ARCH=NO | xcpretty
 - pod lib lint