Add CsvSourceIterator, XmlExcelWriter, XmlExcelSourceIterator

Add CsvWriter, XmlExcelWriter, XmlExcelSourceIterator

[CsvSourceIterator] Parse line by line

[XmlExcelSourceIterator] Use xml sax parser instead of storing into an array

[XmlExcelSourceIterator] Write only on buffer

Add tests for XmlExcel*

Apply PHP-CS-Fixer

Add XmlSourceIterator

Create AbstractXmlSourceIterator

Add support for "ss:" namespace prefixed XmlExcel file

[XmlExcelWriter] Add possibility to define cells type
Merge branch 'master' of github.com:vincenttouzet/exporter