set db engine explicitly on url scheme

bin/compile

@@ -52,7 +52,6 @@ try:
         urlparse.uses_netloc.append('mysql')
         url = urlparse.urlparse(os.environ['DATABASE_URL'])
         DATABASES['default'] = {
-            'ENGINE':   'django.db.backends.postgresql_psycopg2',
             'NAME':     url.path[1:],
             'USER':     url.username,
             'PASSWORD': url.password,