Update SubmittingPatches.
Update SubmittingPatches.

- It does not matter how I read git list.  What matters is that
  I do not necessarily read everything on it.

- Talk a bit about how to use applymbox to check one's own
  patches.

- Talk a bit about PGP signed patches.

Signed-off-by: Junio C Hamano <dc50d1021234060e53ec42a77d526afa2fe07479@cox.net>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git