There are many types of tags used in S-o-b area [1].
Update the regex to handle them properly. It requires
the tag should be started by a capital letter and ended
by '-by: ' or '-By: '. The only exception is 'Cc: '.
[1] http://lwn.net/Articles/503829/
Signed-off-by: Namhyung Kim <namhyung@kernel.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>