add coverage in tox for codecov
add coverage in tox for codecov

slav0nic/DjangoBB,slav0nic/DjangoBB,hsoft/DjangoBB,hsoft/slimbb,hsoft/DjangoBB,hsoft/slimbb,hsoft/slimbb,slav0nic/DjangoBB,hsoft/DjangoBB