Update Twitter name and logo

[psjnek]

Twitter was renamed and has a logo now. I suggest that we update the logo in the header.
I would also love to work on this issue.

[dhmlau]

@WebSnke, sounds good to me. Thanks!

[Icarus-05]

hey @WebSnke I would like to help fix this issue. Can u assign it to me ?

[dhmlau]

@Icarus-05, please feel free to submit a PR. Thanks!

[GrooveCS]

@dhmlau, Can we have the label set to doc?

[dhmlau]

@GrooveCS, thanks for looking into this. I'm not sure if there's a need to set the label to docs. Are you thinking of categorizing the issues that you're reporting?