cs fix

Behavioral/Iterator/BookList.php

@@ -13,7 +13,7 @@ class BookList implements \Countable
             return $this->books[$bookNumberToGet];
         }
 
-        return NULL;
+        return null;
     }
 
     public function addBook(Book $book)

Behavioral/Iterator/BookListIterator.php

@@ -74,4 +74,4 @@ class BookListIterator implements \Iterator
     {
         $this->currentBook = 0;
     }
-}
+}

Behavioral/Iterator/BookListReverseIterator.php

@@ -20,4 +20,4 @@ class BookListReverseIterator extends BookListIterator
     {
         return 0 <= $this->currentBook;
     }
-}
+}

Behavioral/Iterator/IteratorTest.php

@@ -63,4 +63,4 @@ class IteratorTest extends \PHPUnit_Framework_TestCase
             $iterator->next();
         }
     }
-}
+}