Added a unique index for case-insensitive username lookups.
Introduced pseudo-deletions as a model and prepared to implement a more advanced api-key/csrf-token policy system.
Updated docs.
Made class replacement more efficient in SequencedQuerySet. There's nearly zero overhead now.
Wrote the middleware class for checking security requirements, but now I'm considering moving those checks elsewhere and dropping the new middleware class.
Refactoring and minor details.