Create banners for all repositories

We were thinking about using something like this:


Maybe we can do something with that stamp like coala logo and meld in some other logo - e.g. a lightning for quickstart. That would be put on the left I guess with plain and simply the project name beneath it.

Opened via [gitter](https://gitter.im/coala/coala/?at=5805daad36d64226368026d9) by @sils

Start by reviewing artwork/background/coala.png and the linked Gitter discussion for the intended visual direction. Identify the repositories that need banners and confirm the banner dimensions and naming expectations with maintainers. Done means each repository has a banner using the coala and project branding described in the issue.

Written by the indexing model from the issue text.