[PATCH docs] Add doc for contribution guidelines

[Sam Mendoza-Jonas]

On Thu, Jan 14, 2016 at 03:10:09AM -0600, OpenBMC Patches wrote:
> From: Jeremy Kerr <jk at ozlabs.org>
<snip>
> +OpenBMC has quite a module structure, consisting of small daemons with a
> +limited set of responsibilities. These communicate over dbus with other
> +components, to implement the complete BMC system.
<snip>

Just a nitpick: should that be s/module/modular?