Add run on repl.it badge to README (#21)

This pull request adds a  badge to the . This will allow users to easily run this repository in their browser, without having to set up an environment. You can learn more about Repl.it [here](https://repl.it).

Author: OrderAndCh4oS

.replit

@@ -1 +1 @@
-run = "python rummy/play.py"
+run = "python rummy/play.py"

README.md

@@ -1,5 +1,6 @@
 [![License: MIT](https://img.shields.io/badge/License-MIT-yellow.svg)](https://opensource.org/licenses/MIT)
 [![Build Status](https://travis-ci.org/sarcoma/Python-Rummy.svg?branch=master)](https://travis-ci.org/sarcoma/Python-Rummy) [![codecov](https://codecov.io/gh/sarcoma/Python-Rummy/branch/master/graph/badge.svg)](https://codecov.io/gh/sarcoma/Python-Rummy)
+[![Run on Repl.it](https://repl.it/badge/github/sarcoma/Python-Rummy)](https://repl.it/github/sarcoma/Python-Rummy)
 
 # Command Line Rummy in Python 3