Update README

Author: andreynering

README.md

@@ -1,4 +1,7 @@
-[![Join the chat at https://gitter.im/go-task/task](https://badges.gitter.im/go-task/task.svg)](https://gitter.im/go-task/task?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+[![License](https://img.shields.io/github/license/go-task/task.svg)](https://github.com/go-task/task/blob/master/LICENSE)
+[![Join the chat at https://gitter.im/go-task/task](https://img.shields.io/gitter/room/go-task/task.svg)](https://gitter.im/go-task/task?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
+[![Join Slack room](https://img.shields.io/badge/%23task%20on-gophers%20slack-blue.svg)](https://gophers.slack.com/messages/task)
+[![Github All Releases](https://img.shields.io/github/downloads/go-task/task/total.svg)](https://github.com/go-task/task/releases)
 [![Build Status](https://travis-ci.org/go-task/task.svg?branch=master)](https://travis-ci.org/go-task/task)
 
 # Task - Simple task runner / "Make" alternative