Add AR associations for task-report

the task_id column already existed
this just sets the relationship

[Story #50902923]
Add spec
Merge pull request #28 from rapid7/feature/task_assoc/reports

Specs for MDM, Pro and MSF passing, [Delivers #50902923]
Merge branch 'master' into feature/specs/spec_catchup
pull latest changes and add report spec
add nessus_fingerprint factory