Go to https://dnsimple.com/r/ecc41c23013629 and open an account.
They have a one click set up for heroku and you can set the TTL to as low as one minute.
Then on the GoDaddy side just change the dns servers from the go daddy servers to the dnsimple ones(all explained on the dnsimple site). SIMPLE ;)
Your domain is still hosted by GoDaddy
GoDaddy is not the place to be managing you dns in my humble opinion.
