Upgrade to sinatra 1.4.0.d
[routing] Use type from accept_entry directly in 1.4.0
[core] Fix layouts, Sinatra 1.4 interprets a nil layout as a false layout
[core] Fix routing test to use not_found callback
[core] Adds 403 custom test
[core] Fixes issue with handling exceptions in after filter
[cache] Fixes nil issue in memcached store tests