Add nbitems to Feed

It avoid multiple query by doctrine to fetch the related data from FeedItem
Update deps (again)
Fix some tests
Remove api.f43.me

- add moar tests
- fix `gzdecode`
- cleanup travis
Adjust travis
Test event
Cleanup delete form & fix some tests
When building, perform the composer install before everything
Fix SimplePieProxy test
CS
Update deps
Add php 5.6 to travis
Cleanup code & remove deprecated method
Remove UrlToAbsolute & use absolute-url-deriver
Fix typo in Constraint RSS
Cleanup
Remove php 5.3 from travis

Since `absolute-url-deriver` require php >= 5.4
Still some cleanup
Still cleanup (thanks to scrutinizer)
Add more tests