README.md update

Example PHPUnit command to run all tests

Author: likel

README.md

@@ -38,8 +38,7 @@ Run [src/example.php](src/example.php) and check your database
 Run [test/SessionHandlerTest.php](test/SessionHandlerTest.php) and [test/SessionDBTest.php](test/SessionDBTest.php) with PHPUnit
 
 ```
-$ phpunit test/SessionHandlerTest.php
-$ phpunit test/SessionDBTest.php
+$ phpunit test
 ```
 
 ## Author