Filter items to keep only new ones since last hit

Issue/390 (#397)

* Fiter items through `Result`. Fix #390

* Fix coding style

* remove backslash

* Advertise filtering ability

Expose accurate mime-types for XML streams

thanks to @boris-glumpler

replace calls to `getDescription()`

v4.9.13

replace `getDescription()` with getContent()` - fix #391 (#395)

feed-io complies with PSR/Log 1 -> 3

v5.0.10

feed-io complies with PSR/Log 1 -> 3 and Monolog 1 -> 2 (#389)

Fix missing media type

v5.0.9

Fix #361 (#387)

Fix missing media type

v4.9.12

Fix #361 (#386)

Use app's autoloader if present

Issue/fix factory (#384)

* Fix missing `use` statement

* Use app's autoloader if present

Autoload the Factory to fix bin/feedio

v5.0.7

Fix missing `use` statement (#383)

Executable doesn't depend on Symfony anymore

Issue/symfony console removal close #377 (#382)

* `./bin/feedio` doesn't need Symfony anymore

* Removed useless stuff

* New Lint rules applied

Cast the length to comply with ints provided by JSON Feed

v5.0.5

Cast the length to comply with ints provided by JSON Feed #374 (#380)