Fix travis build error

Author: Bruce-pac

.travis.yml

@@ -8,7 +8,7 @@ cache: cocoapods
 podfile: Example/Podfile
 before_install:
 - gem install cocoapods # Since Travis is not always on latest version
-- pod install --project-directory=Example
+- pod install --repo-update --project-directory=Example
 script:
 - set -o pipefail && xcodebuild test -enableCodeCoverage YES -workspace Example/RxIGListKit.xcworkspace -scheme RxIGListKit-Example -sdk iphonesimulator9.3 ONLY_ACTIVE_ARCH=NO | xcpretty
 - pod lib lint