electronをインストールするためにnpm install -g electron-prebuiltするとErrorが起こってしまいます。
どうすればいいのでしょうか?

sudo npm install -g electron-prebuiltを実行すると下のようなErrorがでます。
sudoで実行しているのにpermission deniedが出ているのはどういうことがおこっているのでしょうか?

io.jsは3.2.0を使っていて、electronは最新を使いたいと思っています。

error.txt


/usr/local/lib/node_modules/electron-prebuilt/install.js:15
  throw err
  ^

Error: EACCES: permission denied, rename '/usr/local/lib/node_modules/electron-prebuilt/electron-tmp-download-10190-1440591106010/electron-v0.30.6-darwin-x64.zip' -> '/Users/user_name/.electron/electron-v0.30.6-darwin-x64.zip'
    at Error (native)
npm ERR! Darwin 14.5.0
npm ERR! argv "/usr/local/bin/iojs" "/usr/local/bin/npm" "install" "-g" "electron-prebuilt"
npm ERR! node v3.2.0
npm ERR! npm  v2.14.0
npm ERR! code ELIFECYCLE

npm ERR! electron-prebuilt@0.30.6 postinstall: `node install.js`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the electron-prebuilt@0.30.6 postinstall script 'node install.js'.
npm ERR! This is most likely a problem with the electron-prebuilt 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 their info via:
npm ERR!     npm owner ls electron-prebuilt
npm ERR! There is likely additional logging output above.

npm ERR! Please include the following file with any support request:
npm ERR!     /Users/user_name/npm-debug.log