Source js files are not included in npm package for v4

Created by: s7b4

Hi,

When we install bootstrap 3.3.6 with npm, source js directory is included but no more with the v4

with both of the following commands: npm install twbs/bootstrap#v4-dev or npm install bootstrap@4.0.0-alpha.2

I get this folder content

├ node_modules/bootstrap/
├── CHANGELOG.md
├── dist
├── grunt
├── Gruntfile.js
├── LICENSE
├── package.json
├── README.md
├── scss

No source js files are present.

Regards Stéphane