Better support for Date custom format (#316)

- To determine if a style should apply a date format, the presence of "applyNumberFormat" attribute on the "cellXfs" section of styles.xml is now optional. We only look at the "numFmtId" attribute (but early return if "applyNumberFormat" is set to "0").
- The format code can contain lowercase AND now uppercase characters as its pattern.
- "General" format code used as a custom format is now supported. It seems to be used by a bunch of programs...

tests/Spout/Reader/XLSX/ReaderTest.php

@@ -279,6 +279,21 @@ class ReaderTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals($expectedRows, $allRows);
     }
 
+    /**
+     * @return void
+     */
+    public function testReadShouldApplyCustomDateFormatNumberEvenIfApplyNumberFormatNotSpecified()
+    {
+        $shouldFormatDates = true;
+        $allRows = $this->getAllRowsForFile('sheet_with_custom_date_formats_and_no_apply_number_format.xlsx', $shouldFormatDates);
+
+        $expectedRows = [
+            // "General", "GENERAL", "MM/DD/YYYY", "MM/dd/YYYY", "H:MM:SS"
+            ['42382', '42382', '01/13/2016', '01/13/2016', '4:43:25'],
+        ];
+        $this->assertEquals($expectedRows, $allRows);
+    }
+
     /**
      * @return void
      */