utils.bitcoin: Add validate() function for API compatibility
utils.bitcoin: Add validate() function for API compatibility

This function was provided by python-bitcoinaddress-0.2.2.tar.gz

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