Jetpack: Bump 'Tested up to' to 4.0 in both trunk and our stable release, as per Otto.

https://twitter.com/otto42/status/504747337491951616



git-svn-id: https://plugins.svn.wordpress.org/jetpack/trunk@974314 b8457f37-d9ea-0310-8a92-e5e31aec5664