Redis Seeds are no longer needed
Added deletion in Bag of Words
Added DELETE HTTP verb support in request context
Updated dossier endpoint spec to cover the DELETE case
Added description of the delete use case in the acceptance tests
Added user authentication feature
Changed encryption algorithm to AES 256
Added validate session functionality to AuthenticationController
request helper methods require now a hash with data instead of fixed payload attributes
Added authentication for /words endpoints and updated specs
Added session spec
Refactored Token class and Session.

Session raises a AuthenticationFailedError exception in case the authentication fails.
Delegated the exception time management to the Token.
Updated specs to cover both features.