$ git clone https://github.com/berlinermorgenpost/cogran.git
$ cd cogran/
$ npm install
$ ./index.js
/tmp/cogran/index.js:11
let optimist = require('optimist');
^^^
SyntaxError: Unexpected strict mode reserved word
at Module._compile (module.js:439:25)
at Object.Module._extensions..js (module.js:474:10)
at Module.load (module.js:356:32)
at Function.Module._load (module.js:312:12)
at Function.Module.runMain (module.js:497:10)
at startup (node.js:119:16)
at node.js:935:3
On Archlinux with npm@2.14.1