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
Merge pull request #1114 from padrino/sinatra_1_4_compat

Sinatra 1.4 compatibility
Merge remote-tracking branch 'upstream/master' into super-admin

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