Filipe Silva 1e476577c1 fix(@angular/cli): don't fail install due to node-sass (#5282)
This change should reduce the amount of problems on npm installs.

It makes the `node-sass` dependency optional, and so install will not fail when it cannot be installed.

For projects that do not use sass, there is no side-effect of an failed node-sass install.

For projects that do use node-sass and the install failed, they should see the following self-explanatory error message:

```
ERROR in ./src/app/app.component.scss
Module build failed: Error: Missing binding D:\sandbox\master-project\node_modules\node-sass\vendor\win32-x64-51\binding.node
Node Sass could not find a binding for your current environment: Windows 64-bit with Node.js 7.x

Found bindings for the following environments:

This usually happens because your environment has changed since running `npm install`.
Run `npm rebuild node-sass` to build the binding for your current environment.
    at module.exports (D:\sandbox\master-project\node_modules\node-sass\lib\binding.js:15:13)
    at Object.<anonymous> (D:\sandbox\master-project\node_modules\node-sass\lib\index.js:14:35)
```

Fix #4429
2017-03-16 20:02:51 +00:00
..
2017-02-01 12:16:09 -08:00