Ask first when deploying to a node that has previously had a newer platform version

(1) grab sha1 from remote server (2) check to see if the hash of the version you are deploying is in the local tree for leap_platform, if #1 and #2 match, go ahead and deploy, otherwise check to see if #1 is in the git tree somewhere, if it is, it is older, if it is not it is newer (3) if older, give a warning and ask if you want to proceed

(from redmine: created on 2013-02-06, relates #1744 (closed))