Library forces users to create components as Pure Components

[kartiksharma1607]

When using withStyles, library wraps React Component into a Pure Component.

https://github.com/kriasoft/isomorphic-style-loader/blob/master/src/withStyles.js#L17

This is done irrespective of user's preference. If user had created a normal React Component it should wrap it into a impure React Component. It should only wrap component into Pure Component if, user's component is itself a pure component.