Add figaro gem
Add pry and pry-remote
Add zendesk_api gem
Ticket model: allow nils in type, priority and status values
Validate presence of ticket's subject and description
Ticket's tags writer
ZendeskClient
Add comment about inheritance_column
Rename external_id to zendesk_id
Remove external_id methods
Check for uniqueness by zendesk_id
Order tickets by updated_at
Set time zone
Fix ticket search sorting
Add forgotten helper
ZendeskClient.create_ticket
Tickets controller: create tickets through ZendeskClient