add ability to add a commit comment when snapshotting

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
add Makefile

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>
finish code to allow snapshot comment

Signed-off-by: Serge Hallyn <serge.hallyn@ubuntu.com>