doc: Convert the afr translator documentation to markdown

Change-Id: I328986812df7adc849fa11b53ae483c2cd0825e8
Signed-off-by: Lubomir Rintel <lubo.rintel@gooddata.com>
Reviewed-on: http://review.gluster.org/5484
Reviewed-by: Vijay Bellur <vbellur@redhat.com>
Tested-by: Vijay Bellur <vbellur@redhat.com>