Issue title: Exampled Doesn't Work
 Issue body: **Env**
I am running OSX El Capitan  Node v4.4.2

**Actions** 
- `git clone` Project

- `cd` into project

- run `npm install`

- run `npm start`

**Error**
```
npm ERR! Darwin 15.6.0
npm ERR! argv "/usr/local/bin/node" "/usr/local/bin/npm" "start"
npm ERR! node v4.4.2
npm ERR! npm  v2.15.0
npm ERR! code ELIFECYCLE
npm ERR! sarah66@example.com start: `webpack-dev-server --config webpack-dev-server.config.js --progress --inline --colors`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the sarah66@example.com start script 'webpack-dev-server --config webpack-dev-server.config.js --progress --inline --colors'.
npm ERR! This is most likely a problem with the material-ui-example-webpack package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR!     webpack-dev-server --config webpack-dev-server.config.js --progress --inline --colors
npm ERR! You can get information on how to open an issue for this project with:
npm ERR!     npm bugs material-ui-example-webpack
npm ERR! Or if that isn't available, you can get their info via:
npm ERR!
npm ERR!     npm owner ls material-ui-example-webpack
npm ERR! There is likely additional logging output above.

npm ERR! Please include the following file with any support request:
npm ERR!     /Users/thom/Desktop/pixs/material-ui-webpack-example/npm-debug.log
```
 Comments: 
 Comment 0: I'm not sure we support node v4. Could you try with a newer version?
 Comment 1: Also, make sure that the port webpack is trying to listen to is free (3000)
 Comment 2: Yeah the issue was the node v4. I updated that and it all worked perfectly. 
 Comment 3: Thanks for letting us know!
{'source': 'GithubIssues', 'repo_name_with_owner': 'callemall/material-ui-webpack-example', 'issue_id': 242542142, 'repo_stars': 338.0}