Fix: Do not add json-loader for Webpack 2
Fix: Do not add json-loader for Webpack 2

Webpack 2 includes it by default

sapegin/react-styleguidist,styleguidist/react-styleguidist,sapegin/react-styleguidist,bluetidepro/react-styleguidist,styleguidist/react-styleguidist,styleguidist/react-styleguidist