Update requirements.txt
Update requirements.txt

Travis was encountering errors because of the requirements file.

studio666/gratipay.com,gratipay/gratipay.com,mccolgst/www.gittip.com,gratipay/gratipay.com,studio666/gratipay.com,eXcomm/gratipay.com,eXcomm/gratipay.com,mccolgst/www.gittip.com,gratipay/gratipay.com,mccolgst/www.gittip.com,gratipay/gratipay.com,eXcomm/gratipay.com,studio666/gratipay.com,studio666/gratipay.com,eXcomm/gratipay.com,mccolgst/www.gittip.com