an existing coverage object to submit, if NULL,
package_coverage will be called with the arguments from
...
repo_token
The secret repo token for your repository,
found at the bottom of your repository's page on Coveralls. This is useful
if your job is running on a service Coveralls doesn't support out-of-the-box.
If set to NULL, it is assumed that the job is running on travis-ci
service_name
the CI service to use, if environment variable
‘CI_NAME’ is set that is used, otherwise ‘travis-ci’ is used.