[FIX] Added missing jade loader

[XavierLeTohic]

Fixed missing loader jade error when running "gulp build" command into webpack production configuration.

ERROR in ./src/components/Header/Header.jade
Module parse failed: /Users/vav/Documents/nestor/react-stylus-webpack-boilerplate/src/components/Header/Header.jade Unexpected token (1:12)
You may need an appropriate loader to handle this file type.

And added .idea into .gitignore