Add an optional "active_installs" field. This should be an positive i…

…nteger that indicates how many sites use your plugin. WordPress will show it in the "view version 1.2.3 details" pop-up. For example, if you set it to 10000, users will see "Active Installs: 10,000+".

  
 Note that wordpress.org itself reports approximate install stats - e.g. 10000 instead of 11450. It's up to you whether you want to do the same, show the exact number of installs, or omit this field entirely.

plugin-update-checker.php

@@ -885,6 +885,7 @@ class PluginInfo_2_0 {
 	public $rating;
 	public $num_ratings;
 	public $downloaded;
+	public $active_installs;
 	public $last_updated;
 
 	public $id = 0; //The native WP.org API returns numeric plugin IDs, but they're not used for anything.
@@ -944,7 +945,7 @@ public function toWpFormat(){
 		//as those returned by the native WordPress.org API. These can be assigned directly. 
 		$sameFormat = array(
 			'name', 'slug', 'version', 'requires', 'tested', 'rating', 'upgrade_notice',
-			'num_ratings', 'downloaded', 'homepage', 'last_updated',
+			'num_ratings', 'downloaded', 'active_installs', 'homepage', 'last_updated',
 		);
 		foreach($sameFormat as $field){
 			if ( isset($this->$field) ) {