SubmittingPatches: who am I and who cares?

SubmittingPatches: who am I and who cares?

The introductory text in the "long version" talks about the origin
of this document with "I started ...", but it is unclear who that I
is, and more importantly, it is not interesting how it was started.

Just state the purpose of the document to help readers decide if it
is releavant to them.

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