Option to return formatted dates instead of PHP objects (#226)

When reading spreadsheets, Spout should be able to return formatted dates, as shown when opened with Excel for instance.
It currently only returns DateTime/DateInterval objects, making it impossible to read + write, as the Writer does not accept objects.

tests/Spout/Reader/ODS/ReaderTest.php

@@ -164,6 +164,21 @@ class ReaderTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals($expectedRows, $allRows);
     }
 
+    /**
+     * @return void
+     */
+    public function testReadShouldSupportFormatDatesAndTimesIfSpecified()
+    {
+        $shouldFormatDates = true;
+        $allRows = $this->getAllRowsForFile('sheet_with_dates_and_times.ods', $shouldFormatDates);
+
+        $expectedRows = [
+            ['05/19/2016', '5/19/16', '05/19/2016 16:39:00', '05/19/16 04:39 PM', '5/19/2016'],
+            ['11:29', '13:23:45', '01:23:45', '01:23:45 AM', '01:23:45 PM'],
+        ];
+        $this->assertEquals($expectedRows, $allRows);
+    }
+
     /**
      * @return void
      */
@@ -455,14 +470,16 @@ class ReaderTest extends \PHPUnit_Framework_TestCase
 
     /**
      * @param string $fileName
+     * @param bool|void $shouldFormatDates
      * @return array All the read rows the given file
      */
-    private function getAllRowsForFile($fileName)
+    private function getAllRowsForFile($fileName, $shouldFormatDates = false)
     {
         $allRows = [];
         $resourcePath = $this->getResourcePath($fileName);
 
         $reader = ReaderFactory::create(Type::ODS);
+        $reader->setShouldFormatDates($shouldFormatDates);
         $reader->open($resourcePath);
 
         foreach ($reader->getSheetIterator() as $sheetIndex => $sheet) {