Add Investigate response structures + tests
Add MaliciousDomain type + tests
Update methods to use new structures + tests
Fix case where lists are empty
Fix DomainResourceRecordFeatures types
response_types: Change RelatedDomainsList to an actual list
response_type: change CooccurrenceList to an actual list
Remove commented out old test
Update README to accommodate new response structures.
Merge branch 'v2.0.0'