Clarify commit message format in contributing guide (#1643)
Clarify commit message format in contributing guide (#1643)

RELEASE_NOTES=n/a

Signed-off-by: Tom Payne <d1448646e260e695ce28b0816a2223f35b207838@gmail.com>
gopasspw/gopass,gopasspw/gopass,franciscocpg/gopass,justwatchcom/gopass