Use better default values to support repositories without sets
Make sure repositories w/o sets get through
Refactoring of harvester to use ListIdentifier/GetRecord
Remove query note from README
Check for code complexity
Fix linting errors
Reduce complexity of import_stage
Add travis ci build badge
Make sure exception don't kill the harvester
Allow harvesting of only one specific set

To harvest only a specific set, you have to add {"set": "name-of-set"}
to the configuration section of the harvest source.
Merge pull request #5 from openresearchdata/support-no-sets

Add support for repositories without sets