added support for database expressions.

laravel/database/expression.php

@@ -0,0 +1,43 @@
+<?php namespace Laravel\Database;
+
+class Expression {
+
+	/**
+	 * The value of the database expression.
+	 *
+	 * @var string
+	 */
+	protected $value;
+
+	/**
+	 * Create a new database expression instance.
+	 *
+	 * @param  string  $value
+	 * @return void
+	 */
+	public function __construct($value)
+	{
+		$this->value = $value;
+	}
+
+	/**
+	 * Get the string value of the database expression.
+	 *
+	 * @return string
+	 */
+	public function get()
+	{
+		return $this->value;
+	}
+
+	/**
+	 * Get the string value of the database expression.
+	 *
+	 * @return string
+	 */
+	public function __toString()
+	{
+		return $this->get();
+	}
+
+}