Make Collection splice return new static.

src/Illuminate/Support/Collection.php

@@ -378,7 +378,7 @@ public function slice($offset, $length = null, $preserveKeys = false)
	 */
	public function splice($offset, $length = 0, $replacement = array())
	{
		array_splice($this->items, $offset, $length, $replacement);
		return new static(array_splice($this->items, $offset, $length, $replacement));
	}

	/**

tests/Support/SupportCollectionTest.php

@@ -245,15 +245,16 @@ public function testSplice()
	{
		$data = new Collection(array('foo', 'baz'));
		$data->splice(1, 0, 'bar');
		$this->assertEquals(array('foo', 'bar', 'baz'), array_values($data->all()));
		$this->assertEquals(array('foo', 'bar', 'baz'), $data->all());

		$data = new Collection(array('foo', 'baz'));
		$data->splice(1, 1);
		$this->assertEquals(array('foo'), array_values($data->all()));
		$this->assertEquals(array('foo'), $data->all());

		$data = new Collection(array('foo', 'baz'));
		$data->splice(1, 1, 'bar');
		$this->assertEquals(array('foo', 'bar'), array_values($data->all()));
		$cut = $data->splice(1, 1, 'bar');
		$this->assertEquals(array('foo', 'bar'), $data->all());
		$this->assertEquals(array('baz'), $cut->all());
	}

	public function testGetListValueWithAccessors()