use shields.io to show the coveralls badge
use shields.io to show the coveralls badge

to avoid aggressive caching by Github (shields.io seems to add `Expires:` to the header)
SpatialMetabolomics/SM_distributed,METASPACE2020/sm-engine,METASPACE2020/sm-engine,SpatialMetabolomics/SM_distributed,SpatialMetabolomics/SM_distributed,SpatialMetabolomics/SM_distributed