Fix Chunk.modules DeprecationWarning in Webpack 3.x

[steven-pribilinskiy]

Updates to Chunk.mapModules is not backwards compatible with Webpack 2.x due to breaking changes in webpack/webpack#4764

Following should be added to README:

Install

# for webpack 3
npm install --save-dev extract-text-webpack-plugin
# for webpack 1, 2
npm install --save-dev extract-text-webpack-plugin@0.1.0

[steven-pribilinskiy]

devDependencies needs to be updated too for CI

[ghost]

Please merge...

[steven-pribilinskiy]

@ddeboer-axtion only the owner of the repo @mariusbalcytis can do that

[ghost]

Yeah i know, I was hoping he would read the message ;)

[mariusbalcytis]

Thanks for the pull request and sorry for the delay.

[steven-pribilinskiy]

ah, even don't mention it )

[arianrhodsandlot]

Bad news: forEachModule is also deprecated as described here: webpack/webpack#6367 😭