travis: show git --version instead

It seems that configuration has no problem:

    core.repositoryformatversion=0
    core.filemode=true
    core.bare=false
    core.logallrefupdates=true
    remote.origin.url=git://github.com/clear-code/git-utils.git
    remote.origin.fetch=+refs/heads/master:refs/remotes/origin/master
    branch.master.remote=origin
    branch.master.merge=refs/heads/master