update README for CSP mode
update README for CSP mode

Polymer/tools,addyosmani/vulcanize,bendroid/vulcanize,Polymer/tools,Polymer/polymer-bundler,Polymer/tools,wprl/spock,threeday0905/vulcanize,Polymer/tools,Polymer/polymer-bundler,rcorp/vulcanize,rcorp/vulcanize,bendroid/vulcanize,threeday0905/vulcanize,Polymer/polymer-bundler