Expose a way to pass params for express.static?

[hirokith]

In https://github.com/webpack/webpack-dev-server/blob/master/lib/Server.js#L203,

// route content request
app.get("*", express.static(contentBase), serveIndex(contentBase));

Now I want to pass param {index: false} to express.static so that it looks like express.static(contentBase, {index: false}) to disable directory indexing, because it makes me feel inconvenient to access other html files under the directory.

Thank you!

[SpaceK33z]

Fixed with #385, which will be part of the next 1.x release.