Fixes #43

I've decided to put the version information in the footer rather than general information, just to tuck it away a bit.

Also bumped up the version in preparation for a small tagged release.

index.php

@@ -8,7 +8,7 @@ namespace OpcacheGui;
  * A simple but effective single-file GUI for the OPcache PHP extension.
  *
  * @author Andrew Collington, andy@amnuts.com
- * @version 2.5.0
+ * @version 2.5.1
  * @link https://github.com/amnuts/opcache-gui
  * @license MIT, http://acollington.mit-license.org/
  */
@@ -54,6 +54,8 @@ header('Pragma: no-cache');
 
 class OpCacheService
 {
+    const VERSION = '2.5.1';
+
     protected $data;
     protected $options;
     protected $defaults = [
@@ -416,7 +418,7 @@ $opcache = OpCacheService::init($options);
 </div>
 
 <footer>
-    <a href="https://github.com/amnuts/opcache-gui" target="_blank">https://github.com/amnuts/opcache-gui</a>
+    <a href="https://github.com/amnuts/opcache-gui" target="_blank" title="opcache-gui (currently version <?php echo OpCacheService::VERSION; ?>) on GitHub">https://github.com/amnuts/opcache-gui - version <?php echo OpCacheService::VERSION; ?></a>
 </footer>
 
 <script type="text/javascript">