README: add ga beacon
README: add ga beacon
bendroid/vulcanize,Polymer/polymer-bundler,Polymer/tools,rcorp/vulcanize,wprl/spock,rcorp/vulcanize,Polymer/tools,threeday0905/vulcanize,bendroid/vulcanize,Polymer/tools,Polymer/polymer-bundler,threeday0905/vulcanize,Polymer/polymer-bundler,Polymer/tools