Add Tip4Commit to list of crowdsourcing projects in the readme.
Add Tip4Commit to list of crowdsourcing projects in the readme.

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