There are gruntfile.js and package.json in the project. npm install is used to download the plug-in and report an error.

  node.js, question
pm ERR!  Darwin 15.2.0
 npm ERR!  argv "/usr/local/bin/node" "/usr/local/bin/npm" "install"
 npm ERR!  node v5.10.1
 npm ERR!  npm  v3.8.3
 npm ERR!  code ELIFECYCLE
 npm ERR!  phantomjs@1.9.15 install: `node install.js`
 npm ERR!  Exit status 1
 npm ERR!
 npm ERR!  Failed at the phantomjs@1.9.15 install script 'node install.js'.
 npm ERR!  Make sure you have the latest version of node.js and npm installed.
 npm ERR!  If you do, this is most likely a problem with the phantomjs package,
 npm ERR!  not with npm itself.
 npm ERR!  Tell the author that this fails on your system:
 npm ERR!  node install.js
 npm ERR!  You can get information on how to open an issue for this project with:
 npm ERR!  npm bugs phantomjs
 npm ERR!  Or if that isn't available, you can get their info via:
 npm ERR!  npm owner ls phantomjs
 npm ERR!  There is likely additional logging output above.
 npm ERR!  Please include the following file with any support request:
 npm ERR!  /Users/mac/Downloads/origin-master/assets/npm-debug.log

It seems notphantomjs@1.9.15This module
You can try to install this module separately.npm install phantomjs --save-dev