implementing stream filtering methods #32

To Implement PHP Stream Filtering into the library the following was done:

* Lazy loading was implemented
* Stream Filter Trait was introduced and added to `AbstractCsv`
* Internal rewrite for `AbstractCsv`, `Reader` and `Writer` class
* The documentation has been change to promote Stream Filtering vs using `setEncodingFrom` property and to warn about Stream Filtering capabilities on the `Writer` class.
* added stream filtering examples