Made changes suggested in code review

Author: mcustiel

README.md

@@ -1226,7 +1226,6 @@ class Rectangle extends Shape
 
  public function __construct($width, $height)
  {
- parent::__construct();
  $this->width = $width;
  $this->height = $height;
  }
@@ -1243,7 +1242,6 @@ class Square extends Shape
 
  public function __construct($length)
  {
- parent::__construct();
  $this->length = $length;
  }