Update API implementation link to the proper Drupal module
Update API implementation link to the proper Drupal module

Merged my sandboxed Drupal module with the actual 'Gittip' module so we can coordinate efforts. Updating the link in the API implementation section.
gratipay/gratipay.com,eXcomm/gratipay.com,gratipay/gratipay.com,studio666/gratipay.com,mccolgst/www.gittip.com,eXcomm/gratipay.com,mccolgst/www.gittip.com,studio666/gratipay.com,mccolgst/www.gittip.com,studio666/gratipay.com,eXcomm/gratipay.com,gratipay/gratipay.com,mccolgst/www.gittip.com,eXcomm/gratipay.com,studio666/gratipay.com,gratipay/gratipay.com