Merge branch 'master' of github.com:box/spout into add-phpstan

 Conflicts:

	.travis.yml

	CONTRIBUTING.md

	composer.json

	src/Spout/Common/Entity/Cell.php

	tests/Spout/Writer/ODS/WriterTest.php

tests/Spout/Common/Entity/RowTest.php

@@ -129,6 +129,6 @@ class RowTest extends \PHPUnit\Framework\TestCase
             ->setStyle($this->getStyleMock())
             ->setCells([]);
 
-        $this->assertInternalType('object', $row);
+        $this->assertInstanceOf(Row::class, $row);
     }
 }

tests/Spout/Common/Helper/FileSystemHelperTest.php

@@ -16,7 +16,7 @@ class FileSystemHelperTest extends TestCase
     /**
      * @return void
      */
-    public function setUp()
+    public function setUp() : void
     {
         $baseFolder = \sys_get_temp_dir();
         $this->fileSystemHelper = new FileSystemHelper($baseFolder);