tutorial: update output of git commit

Commit c85db25 changed the format of the message produced
by "git commit" when creating a commit. This patch updates
the example session in the tutorial to the new format.

It also adds in the missing diffstat summary lines, which
should have been added long ago.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

Documentation/gittutorial-2.txt

@@ -32,11 +32,13 @@ Initialized empty Git repository in .git/
 $ echo 'hello world' > file.txt
 $ git add .
 $ git commit -a -m "initial commit"
-Created root-commit 54196cc (initial commit) on master
+[master (root-commit)] created 54196cc: "initial commit"
+ 1 files changed, 1 insertions(+), 0 deletions(-)
  create mode 100644 file.txt
 $ echo 'hello world!' >file.txt
 $ git commit -a -m "add emphasis"
-Created c4d59f3 (add emphasis) on master
+[master] created c4d59f3: "add emphasis"
+ 1 files changed, 1 insertions(+), 1 deletions(-)
 ------------------------------------------------
 
 What are the 7 digits of hex that git responded to the commit with?