Optimize row expanding

[queimadus]

This PR optimizes the row expanding procedure and deal better with rendering React components in the expandedRowRender function by:

• reducing the number of calls to determine if the same row is expanded inside the same render,
• only calling the expandedRowRender function when the row is expanded.
  • this way, a react component mounted here will have the componentDidMount and componentWillUnmount methods correctly called.

It also, fixes an linting error present in the master branch

[yiminghe]

thanks