upgrade dj_inmemorystorage
Avatar compatibility improvements

This adds (for avatars only):
 - Token Authentication as a form variable.
 - POST for update (with disabled CSRF).
Fix DEFAULT_THROTTLE_RATES section of the README
Fix DEFAULT_THROTTLE_RATES docs again
Simplify avatar test
More specific http method delegation
Allow changing of avatars through legacy post
Do not change immutable QueryDict
Update changelog