Cleanup in src/, adding namespaces, removing php closing tag and general code cleanup

src/Numerics/IdentityMatrix.php

@@ -0,0 +1,9 @@
+<?php namespace Moserware\Skills\Numerics;
+
+class IdentityMatrix extends DiagonalMatrix
+{
+    public function __construct($rows)
+    {
+        parent::__construct(array_fill(0, $rows, 1));
+    }
+}