Bump nokogiri to 1.6.8
Number of important security and bug fixes. See: https://github.com/sparklemotion/nokogiri/blob/master/CHANGELOG.md#168--2016-06-06
Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Number of important security and bug fixes. See: https://github.com/sparklemotion/nokogiri/blob/master/CHANGELOG.md#168--2016-06-06