Update features

Author: loopj

README.md

@@ -10,6 +10,8 @@ Features
 - HTTP requests happen **outside the UI thread**
 - Requests use a **threadpool** to cap concurrent resource usage
 - GET/POST **params builder** (RequestParams)
+- **Multipart file uploads** with no additional third party libraries
+- Tiny size overhead to your application, only **22kb** for everything
 - Automatic smart **request retries** optimized for spotty mobile connections
 - Automatic **gzip** response decoding support for super-fast requests
 - Optional built-in response parsing into **JSON** (JsonHttpResponseHandler)