Row objects and Cell styling

This commit introduces Row and Cell entities, that will replace the arrays passed in previously.
It also adds support for Cell styling (instead of Row styling only).

tests/Spout/Writer/XLSX/SheetTest.php

@@ -5,6 +5,7 @@ namespace Box\Spout\Writer\XLSX;
 use Box\Spout\Common\Type;
 use Box\Spout\TestUsingResource;
 use Box\Spout\Writer\Common\Entity\Sheet;
+use Box\Spout\Writer\RowCreationHelper;
 use Box\Spout\Writer\WriterFactory;
 
 /**
@@ -13,6 +14,7 @@ use Box\Spout\Writer\WriterFactory;
 class SheetTest extends \PHPUnit_Framework_TestCase
 {
     use TestUsingResource;
+    use RowCreationHelper;
 
     /**
      * @return void
@@ -91,7 +93,7 @@ class SheetTest extends \PHPUnit_Framework_TestCase
         $sheet = $writer->getCurrentSheet();
         $sheet->setName($sheetName);
 
-        $writer->addRow(['xlsx--11', 'xlsx--12']);
+        $writer->addRow($this->createRowFromValues(['xlsx--11', 'xlsx--12']));
         $writer->close();
 
         return $sheet;
@@ -110,9 +112,9 @@ class SheetTest extends \PHPUnit_Framework_TestCase
         $writer = WriterFactory::create(Type::XLSX);
         $writer->openToFile($resourcePath);
 
-        $writer->addRow(['xlsx--sheet1--11', 'xlsx--sheet1--12']);
+        $writer->addRow($this->createRowFromValues(['xlsx--sheet1--11', 'xlsx--sheet1--12']));
         $writer->addNewSheetAndMakeItCurrent();
-        $writer->addRow(['xlsx--sheet2--11', 'xlsx--sheet2--12', 'xlsx--sheet2--13']);
+        $writer->addRow($this->createRowFromValues(['xlsx--sheet2--11', 'xlsx--sheet2--12', 'xlsx--sheet2--13']));
 
         $writer->close();