git.1: switch homepage for stats

According to http://meta.ohloh.net/2014/07/black-duck-open-hub/
the site name of ohloh changed to openhub.

Change the man page accordingly.

Signed-off-by: Stefan Beller <stefanbeller@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
.mailmap: combine Stefan Beller's emails

Google mail has had the extension @googlemail.com for a long time
in Germany as @gmail.de was already taken by a competitor.
Nowadays the original gmail company isn't there anymore(?), hence
Googlemail also introduced @gmail.com in Germany, which I switched to.

This changed mail address of mine first appeared in 398dd4bd039680b
(2014-07-10, .mailmap: map different names with the same email
address together) ironically.

Signed-off-by: Stefan Beller <stefanbeller@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git 2.0.3

Signed-off-by: Junio C Hamano <gitster@pobox.com>