Allow value of 0 to be passed into POISSON formula
Bug "Undefined variable: options"

There is a bug for the var `$option`:

    Notice: Undefined variable: options in [...]/vendor/phpoffice/phpexcel/Classes/PHPExcel/Settings.php on line 384

This bug is fixed with `self::$_libXmlLoaderOptions == (LIBXML_DTDLOAD | LIBXML_DTDATTR)` instead of `$options == (LIBXML_DTDLOAD | LIBXML_DTDATTR)`
change sequential validation for orientation dompdf
Implement empty ODF archive

Work item CP1930, GH-157
Implements basic writing functionality
Add example
Reduce memory usage after an xls load
Merge branch 'develop' of https://github.com/PHPOffice/PHPExcel into develop
Merge pull request #352 from ke20/patch-1

Bug "Undefined variable: options"
Merge pull request #378 from frost-nzcr4/ft-157-ODF

Add basic ODS writing functionality
Merge pull request #349 from luxbet/poisson_fix

Allow value of 0 to be passed into POISSON formula
Merge pull request #367 from januarsiregar/develop

change sequential validation for orientation dompdf