Added proper cache::forever implementations to each driver.

Signed-off-by: Taylor Otwell <taylorotwell@gmail.com>

laravel/cache/drivers/driver.php

@@ -53,18 +53,6 @@ abstract class Driver {
 	 */
 	abstract public function put($key, $value, $minutes);
 
-	/**
-	 * Write an item to the cache for five years.
-	 *
-	 * @param  string  $key
-	 * @param  mixed   $value
-	 * @return void
-	 */
-	public function forever($key, $value)
-	{
-		return $this->put($key, $value, 2628000);
-	}
-
 	/**
 	 * Get an item from the cache, or cache and return the default value.
 	 *