Update author to indicate project includes other contributors

@laurentkempe has also requested that his name be added to a list of project contributors on the Git Source Control Provider home page. Since the project now has several contributors, it's probably a good idea to start a running list. So far I see the following (alphabetical order after Yiyi as the primary author).

* Yiyi Sun
* Javier Castro
* Tim Chen
* Sean Collins
* Sam Harwell
* Laurent Kempé
* Daniel Pihlstrom
* Duncan Smart
* Eli Young