Test adding taskers "on-the-fly" after flack has started

[jfrioux]

Test the following scenario:

• flack is running
• tasker is added under 'envs/dev/lib/taskers/new-tasker/'
• launch a workflow that uses that tasker
• see if it works or errors

If that works, fill an issue to complete the taskter CRUD (ref: floraison/flack#2)
Otherwise, see why it doesn't.