Vue-material: Aucune version compatible trouvée : extract-text-webpack-plugin@beta

quand j'essaye npm install
j'ai échoué et le message :

npm ERR! code ETARGET
npm ERR! notarget No compatible version found: extract-text-webpack-plugin<strong i="8">@beta</strong>
npm ERR! notarget Valid install targets:
npm ERR! notarget 0.1.0, 0.1.1, 0.1.2, 0.2.0, 0.2.1, 0.2.2, 0.2.3, 0.2.4, 0.2.5, 0.3.0, 0.3.1, 0.3.2, 0.3.3, 0.3.4, 0.3.5, 0.3.6, 0.3.7, 0.3.8, 0.4.0, 0.5.0, 0.6.0, 0.7.0, 0.7.1, 0.8.0, 0.8.1, 0.8.2, 0.9.0, 0.9.1, 1.0.0, 1.0.1, 2.0.0-beta.0, 2.0.0-beta.1, 2.0.0-beta.2, 2.0.0-beta.3, 2.0.0-beta.4, 2.0.0-beta.5, 2.0.0-rc.0, 2.0.0-rc.1, 2.0.0-rc.2, 2.0.0-rc.3, 2.0.0, 2.1.0
npm ERR! notarget 
npm ERR! notarget This is most likely not a problem with npm itself.
npm ERR! notarget In most cases you or one of your dependencies are requesting
npm ERR! notarget a package version that doesn't exist.
npm ERR! notarget 
npm ERR! notarget It was specified as a dependency of 'vue-material'
npm ERR! notarget 

npm ERR! A complete log of this run can be found in:
npm ERR!     ~/.npm/_logs/2017-04-05T09_20_26_040Z-debug.log