added apt-get instructions needed for making certs / keys and for supporting dns
added apt-get instructions needed for making certs / keys and for supporting dns

bridgetkromhout/docs-deploying-cf,cwest/docs-deploying-cf,njbennett/docs-deploying-cf,cloudfoundry/docs-deploying-cf,jpalermo/docs-deploying-cf,shalako/docs-deploying-cf