Refactor src layout, add scheduler

- Add makefiles for building docker images
- Add scheduler, scheduler-web, and scheduler-worker fig containers.
- Refactor src tree layout.
- Add threatinator-run, threatinator-run-all, and threatinator-list
  commands to scheduler container.
Break out tests for each subcomponent
Merge pull request #184 from justfalter/add_scheduler

Refactor src layout, add scheduler