update username string checking code & comments
update username string checking code & comments

now it does what it says on the tin

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