1. Add an argument 'limit' which is intended for limiting tickets in one project (for test purposes)
2. Shorten length of project keys to 10 characters
3. Export milestones as custom fields
4. Fix issue with markup conversion
5. Fix exporting of 'dueDate' field
6. Fix exporting of estimation fields
7. Add exporting of deleted users as well
8. ! Output data as JSON (not as a Ruby hash!)