Add sendOrder column to EmailSend table.
Change identifiers to integer.
Improve triggers to maintain Subscriber.state column.
Use same type for all state columns.
Add state column to EmailSend table.
Do not delete not allowed messages.
Fix addEmail method of the API.
Add sentAt column to EmailSend table.
Add --offset to send worker.
Drop all triggers before new ones.
Use past tense on state columns.
Change trackerImage/ URL to track/.
Add changes of 2.1.