http://stackoverflow.com/questions/18745278/how-to-initialize-gruntfile-js
https://github.com/gruntjs/grunt-init-gruntfile
grunt-init npmとgrunt-init-gruntfileテンプレートを使う．
npm install -g grunt-init git clone https://github.com/gruntjs/grunt-init-gruntfile.git ~/.grunt-init/gruntfile grunt-init gruntfile
