added note about deprecation of slave to agent.
added note about deprecation of slave to agent.

brndnmtthws/dcos-website,ahoskins/dcos-website,ahoskins/dcos-website,ahoskins/dcos-website,brndnmtthws/dcos-website,brndnmtthws/dcos-website,brndnmtthws/dcos-website,ahoskins/dcos-website,dcos/dcos-website,dcos/dcos-website,dcos/dcos-website,dcos/dcos-website