How to plot Dirichlet Function

I'm writting a document in maths and I want to add the graph of the Dirichlet Function. I was googling to find the tikz code of something like that but unfortunately I found nothing...

The graph is what seems in the picture:

I don't know how to plot it in tikz... and a link I found http://ift.tt/1yvzUGX

well while it was compiled... the graph was nowhere to be seen.

So, I would be more than happy if someone could provide me a link where I can copy the cody or draw that for me... I know it's a long shot!