Added position value to tests

This edit fixes 35 errors but introduces 4 failures and leaves 4
unsolved errors.

`Time: 1.2 seconds, Memory: 9.25Mb

There were 4 errors:

1) ClosureTableTestCase::testHasPrevSiblings
InvalidArgumentException: Value must be provided.

./vjandrea/ClosureTable/vendor/illuminate/database/Illuminate/Database/Q
uery/Builder.php:281
./vjandrea/ClosureTable/vendor/illuminate/database/Illuminate/Database/E
loquent/Builder.php:774
./vjandrea/ClosureTable/src/models/Entity.php:483
./vjandrea/ClosureTable/src/models/Entity.php:483
./vjandrea/ClosureTable/src/models/Entity.php:630
./vjandrea/ClosureTable/src/models/Entity.php:620
./vjandrea/ClosureTable/tests/ClosureTableTestCase.php:532

2) ClosureTableTestCase::testCountPrevSiblings
InvalidArgumentException: Value must be provided.

./vjandrea/ClosureTable/vendor/illuminate/database/Illuminate/Database/Q
uery/Builder.php:281
./vjandrea/ClosureTable/vendor/illuminate/database/Illuminate/Database/E
loquent/Builder.php:774
./vjandrea/ClosureTable/src/models/Entity.php:483
./vjandrea/ClosureTable/src/models/Entity.php:483
./vjandrea/ClosureTable/src/models/Entity.php:630
./vjandrea/ClosureTable/tests/ClosureTableTestCase.php:541

3) ClosureTableTestCase::testHasNextSiblings
InvalidArgumentException: Value must be provided.

./vjandrea/ClosureTable/vendor/illuminate/database/Illuminate/Database/Q
uery/Builder.php:281
./vjandrea/ClosureTable/vendor/illuminate/database/Illuminate/Database/E
loquent/Builder.php:774
./vjandrea/ClosureTable/src/models/Entity.php:483
./vjandrea/ClosureTable/src/models/Entity.php:483
./vjandrea/ClosureTable/src/models/Entity.php:672
./vjandrea/ClosureTable/src/models/Entity.php:662
./vjandrea/ClosureTable/tests/ClosureTableTestCase.php:569

4) ClosureTableTestCase::testCountNextSiblings
InvalidArgumentException: Value must be provided.

./vjandrea/ClosureTable/vendor/illuminate/database/Illuminate/Database/Q
uery/Builder.php:281
./vjandrea/ClosureTable/vendor/illuminate/database/Illuminate/Database/E
loquent/Builder.php:774
./vjandrea/ClosureTable/src/models/Entity.php:483
./vjandrea/ClosureTable/src/models/Entity.php:483
./vjandrea/ClosureTable/src/models/Entity.php:672
./vjandrea/ClosureTable/tests/ClosureTableTestCase.php:578

--

There were 4 failures:

1) ClosureTableTestCase::testSiblings
Failed asserting that actual size 4 matches expected size 3.

./vjandrea/ClosureTable/tests/ClosureTableTestCase.php:500

2) ClosureTableTestCase::testPrevSibling
Failed asserting that '1' matches expected 2.

./vjandrea/ClosureTable/tests/ClosureTableTestCase.php:516

3) ClosureTableTestCase::testPrevSiblings
Failed asserting that actual size 4 matches expected size 3.

./vjandrea/ClosureTable/tests/ClosureTableTestCase.php:526

4) ClosureTableTestCase::testCountSiblings
Failed asserting that 4 matches expected 3.

./vjandrea/ClosureTable/tests/ClosureTableTestCase.php:599
`