Add is.gd URL shortening API

README.md

@@ -877,6 +877,7 @@ API | Description | Auth | HTTPS | CORS |
 | [Bitly](http://dev.bitly.com/get_started.html) | URL shortener and link management | `OAuth` | Yes | Unknown |
 | [CleanURI](https://cleanuri.com/docs) | URL shortener service | `No` | Yes | Yes |
 | [ClickMeter](https://support.clickmeter.com/hc/en-us/categories/201474986) | Monitor, compare and optimize your marketing links | `apiKey` | Yes | Unknown |
+| [Is.gd](https://is.gd/developers.php) | URL Shortening API | `No` | Yes | Unknown |
 | [Rebrandly](https://developers.rebrandly.com/v1/docs) | Custom URL shortener for sharing branded links | `apiKey` | Yes | Unknown |
 
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