Add SonarQube coverage support

See #328 
In that case, maybe the color is simply irrelevant. I may be wrong, but I think that most people set up their coverage tool to only look at sensitive code, so that they only need to look whether the badge is less than 100% coverage.

Maybe what people really want to know is whether it has increased or decreased. Maybe the badge should be red in one case, and green in the other.

(I'm a bit surprised that you linked to an article that explained that having a fixed-percentage-driven coverage is pointless; did you mean that this article was wrong?)