fix IRC domain name in `.travis.yml`
fix IRC domain name in `.travis.yml`

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