casperJS screenshot of internal settings popup

Change-Id: Ib6975ce554c039a0d85cd65ee11b2fc0c14e00fb
Reviewed-on: http://review.couchbase.org/37727
Reviewed-by: Pavel Blagodov <stochmail@gmail.com>
Tested-by: Pavel Blagodov <stochmail@gmail.com>