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New Features:
* input/output fields on schema that allow blanks will return None if None was
provided (with possibly default to be set for such cases in the future)
* automated error codes for incoming data validation are possible to override,
change ERROR_CODEBOOK_ATTRIBUTES and ERROR_CODEBOOK_SCHEMA in your local
settings
* add blinker as dependency to allow adding custom signals
* create signals module that will allow emitting signals from magicarp
* first magicarp signal is emitted, it's name is 'shutdown', is being
send only in development mode when shutdown request was received
* add implementation of persistent storage
* add example implementation of /auth endpoint
* add favicon to common endpoints
* add a way to override authentication
* add a way to override registering routes
Breaking Compatibility Changes:
* hooks on magicarp server_factory has been changed from 'before_set_up' to
'before_setup' and 'set_up' into 'setup'
* renamed two functions on server factory to be slightly clearer, one went
from 'before_setup' to 'first_setup' and the other changed from
'after_setup' to 'final_setup'