Add Ganeti CONTRIBUTE.md
Add Ganeti CONTRIBUTE.md

Add CONTRIBUTE.md, which details the contribution process for Ganeti.

Reviewed-on: https://github.com/ganeti/ganeti/pull/40
Signed-off-by: Rafael Marinheiro <98161604651b2a4f5f79def17a703e1568ef5856@google.com>
Reviewed-by: Federico "Morg" Pareschi <ff862f58af48d157b995cd83870fbfa4aec8edf3@google.com>
ganeti/ganeti,mbakke/ganeti,ganeti/ganeti,yiannist/ganeti,yiannist/ganeti,mbakke/ganeti,ganeti/ganeti,yiannist/ganeti,mbakke/ganeti