[CB-3923] 2.8.0 to 2.9.0 upgrade guide, fixed version string in previous upgrade guide
[CB-3752][CB-3753] (2.8.0 Folder) iOS Upgrade Guide is missing instructions for 2.7.0 -> 2.8.0 upgrade
CB-3906: Yay! That was easy!
Merge branch 'master' of https://git-wip-us.apache.org/repos/asf/cordova-docs
Version 2.9.0rc1