Feature request: Support scoped packages

[jhenninger]

Right now, linking scoped packages will fail with an ENOENT because the scope directory does not exist in node_modules:

[npm-workspace] Installing workspace /tmp/npmtest
[npm-workspace] npm install for /tmp/npmtest/A
Error: ENOENT: no such file or directory, mkdir '/tmp/npmtest/B/node_modules/@scopename/A'
    at Error (native)
    at Object.fs.mkdirSync (fs.js:799:18)
    at /home/jo/code/nvm/versions/node/v4.2.1/lib/node_modules/npm-workspace/lib/npm-workspace.js:353:12
[...]

workspace.json:

{
  "links": {
    "@scopename/A": "A"
  }
}