Fix failing CI tests (#460)
Fix failing CI tests (#460)

* bump node version to 6
* use default travis osx_image of xcode9.4
* comment out flakey local test

jeroenv/cheqroom-plugin-inappbrowser,FreshGrade/cordova-plugin-inappbrowser,purplecabbage/cordova-plugin-inappbrowser,tbassett44/cordova-plugin-inappbrowser,jeroenv/cheqroom-plugin-inappbrowser,jeroenv/cheqroom-plugin-inappbrowser,tbassett44/cordova-plugin-inappbrowser,purplecabbage/cordova-plugin-inappbrowser,FreshGrade/cordova-plugin-inappbrowser,apache/cordova-plugin-inappbrowser,apache/cordova-plugin-inappbrowser,purplecabbage/cordova-plugin-inappbrowser,jeroenv/cheqroom-plugin-inappbrowser,apache/cordova-plugin-inappbrowser,FreshGrade/cordova-plugin-inappbrowser,jeroenv/cheqroom-plugin-inappbrowser,tbassett44/cordova-plugin-inappbrowser