New defaults for running javascript

if there is a Gruntfile.js file in the root dir, run yeoman (without params)
if there is a grunt.js file in the root dir, run grunt (without params)
if there is a package.json file in the root dir, run npm test
if there is a index.html in the root dir, open that in a browser
if there is a index.html in the public dir below the root dir run that in a browser
otherwise run current file with node