Add coverage badge

Also we could add the status badge to the GitLab repo. You'll find this under Settings->General I believe. For the badge to be created we would have to added the following to the .gitlab yaml file:

coverage: '/(?i)total.*? (100(?:\.0+)?\%|[1-9]?\d(?:\.\d+)?\%)$/'
  artifacts:
    reports:
      coverage_report:
        coverage_format: cobertura
        path: coverage.xml