git-tar-tree: documentation update

 * add example on how to avoid adding a global extended pax header
 * don't mention linux anymore, use git itself as an example instead
 * update to v1.4.0 ;-)
 * append missing :: to the examples

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <junkio@cox.net>