Add goodbye message

[n-kb]

Add a modal box, to be closed on [X] on top right on on button at the bottom.

Text of box:

Hey there,

In the past 18 months, we worked hard to provide a great tool for network analysis. For a wide variety of reasons, we did not succeed. We will retire Detective.io on 20 August 2015. If you have data stored on the platform, please download it before this date. It will not be available thereafter.

Fortunately, our competitors created fantastic tools, such as Kumu or Grano Project. Check them out.

The Detective.io team

Got it