remove unless_role option and document better solution. fix #66
Merge pull request #64 from ddeboer/configure-cacheable-status

allow configuration to decide on cacheable status of response
catch exceptions during flush for web responses
Merge pull request #54 from ddeboer/catch-exception

catch exceptions during flush for web responses
adding configuration rules for tags
allow to configure tags on routes as constants or with expressions
cleanup configuration
moving validation into configuration class