Merge pull request AllenDowney#3 from jayaprabhakar/master

Add link to source code hosted on Codiva online java ide

Author: AllenDowney

README.md

@@ -7,6 +7,7 @@ Git is a version control system that allows you to keep track of the files that
 A collection of files under Git's control is called a repository.
 
 There are several ways you can work with the code:
+*   You can edit and run the code on [Codiva online java IDE](https://www.codiva.io/tutorials/thinkjavacode).
 
 *   You can create a copy of this repository on GitHub by pressing the "Fork" button in the upper right.
 If you don't already have a GitHub account, you'll need to create one.