'Returns the path of the settings file.'

def build_filename(self):

    p = platform.system()
    if (p == 'Windows'):
        appdata = os.environ['APPDATA']
        return '{}\\OnionShare\\onionshare.json'.format(appdata)
    elif (p == 'Darwin'):
        return os.path.expanduser('~/Library/Application    Support/OnionShare/onionshare.json')
    else:
        return os.path.expanduser('~/.config/onionshare/onionshare.json')
