Add user context implementation
configuration and doc cleanup

fix typo

improving the doc a bit
allow configuration to run with no firewall on some paths. fix #72

cleanups on user context.

fix test

adjust to hash generator refactoring

update doc
Move repository to FriendsOfSymfony
Merge pull request #71 from FriendsOfSymfony/user-context

User context
Upgrade friendsofsymfony/http-cache to alpha3
adding configuration rules for tags
allow to configure tags on routes as constants or with expressions

cleanup configuration

moving validation into configuration class
add overview table to doc

Remove authorization_listener config