Looks like the theme is doing it wrong (simplified code):
define( 'ZIPPY_THEME_BASE_URL', get_template_directory_uri() );
$lang = ZIPPY_THEME_BASE_URL. '/lang';
load_theme_textdomain( 'zippy', $lang );
It's passing an URL and it should be a path, change the load_theme_textdomain
line to:
load_theme_textdomain( 'zippy', get_template_directory() . '/lang');