doc: Convert the coding standards to markdown

Change-Id: I5f3bec7b86ce31beb7459a27dc0f4ba39c6d9610
Signed-off-by: Lubomir Rintel <lubo.rintel@gooddata.com>
Reviewed-on: http://review.gluster.org/5479
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Vijay Bellur <vbellur@redhat.com>