Put back CodeStyle checks

It had been deleted by mistake

.travis.yml

@@ -5,6 +5,8 @@ language: php
 
 matrix:
   include:
+    - php: 7.2
+      env: WITH_CS=true
     - php: 7.2
       env: WITH_PHPUNIT=true
     - php: 7.3

tests/Spout/Writer/ODS/WriterTest.php

@@ -306,8 +306,8 @@ class WriterTest extends TestCase
 
             $this->writeToODSFile($dataRows, $fileName);
 
-            $this->assertValueWasNotWrittenToSheet($fileName, 1, "1234,5");
-            $this->assertValueWasWrittenToSheet($fileName, 1, "1234.5");
+            $this->assertValueWasNotWrittenToSheet($fileName, 1, '1234,5');
+            $this->assertValueWasWrittenToSheet($fileName, 1, '1234.5');
         } finally {
             // reset locale
             \setlocale(LC_ALL, $previousLocale);