Update heroku-config.py

[lswright]

Updated to complete the set command - note the space before and after -a .

[stima-sacco]

After login in from heroku cli,
This line os.system('heroku config:set ' + name + '=' + value) should be replaced with os.system('heroku config:set ' + name + '=' + value + ' --app app-name').
Where app-name is the name of your heroku app