add phantomjs to ci docker image
add phantomjs to ci docker image

Signed-off-by: Toby Rumans <516e7840355d33b790e9dc5c111fe7c7c270a08f@pivotal.io>

simonjjones/atc,zachgersh/atc,pivotal-devin-fallak/atc,savaki/atc,utako/atc,zachgersh/atc,simonjjones/atc,savaki/atc,zachgersh/atc,zachgersh/atc,savaki/atc,utako/atc,pivotal-devin-fallak/atc,utako/atc,pivotal-devin-fallak/atc,simonjjones/atc