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

src/FactorGraphs/KeyedVariable.php

@@ -0,0 +1,18 @@
+<?php namespace Moserware\Skills\FactorGraphs;
+
+class KeyedVariable extends Variable
+{
+    private $_key;
+
+    public function __construct(&$key, $name, &$prior)
+    {
+        parent::__construct($name, $prior);
+        $this->_key = &$key;
+    }
+
+    public function &getKey()
+    {
+        $key = &$this->_key;
+        return $key;
+    }
+}