Added To-Done package for a simple and effective means of creating and managing todo lists

To-Done is a simple tool for creating to do lists. To do lists are just text files with the extension "todo". The functionality of this package is based entirely on a language syntax.

![example-goto](https://f.cloud.github.com/assets/2304337/1650603/cd2e538a-5a9b-11e3-9bed-71f0bbd4b173.png)