send-email docs: add format-patch options

git-send-email(1) does not mention that "git format-patch" options are
accepted. Augment SYNOPSIS and DESCRIPTION to mention it.

Update git-send-email.perl USAGE to be consistent with
git-send-email(1).

Signed-off-by: Thiago Perrotta <tbperrotta@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/git-send-email.perl b/git-send-email.perl
index d34c1af..0408722 100755
--- a/git-send-email.perl
+++ b/git-send-email.perl
@@ -40,7 +40,8 @@
 
 sub usage {
 	print <<EOT;
-git send-email [options] <file | directory | rev-list options >
+git send-email' [<options>] <file|directory>
+git send-email' [<options>] <format-patch options>
 git send-email --dump-aliases
 
   Composing: