Fix npm_module install

[hirocaster]

I can't install npm modules. it's fix bugs.
because pupet exec params miss.

bug report.

  $version = "0.12"
(snip)
  npm_module { 'grunt-cli for ${version}':
    module       => 'grunt-cli',
    node_version => $version,
  }

errors

npm ERR! argv "node" "/opt/nodes/0.12/bin/npm" "install" "grunt-cli@>= 0" "--global"
npm ERR! node v0.12.7
npm ERR! npm  v2.14.0
npm ERR! path /Users/root
npm ERR! code EACCES
npm ERR! errno -13

npm ERR! Error: EACCES, mkdir '/Users/root'
npm ERR!     at Error (native)
npm ERR!  { [Error: EACCES, mkdir '/Users/root'] errno: -13, code: 'EACCES', path: '/Users/root' }
npm ERR!
npm ERR! Please try running this command again as root/Administrator.

[blackjid]

thanks! 👍