updated setup.py for async version in Python 3.5+
updated setup.py for async version in Python 3.5+

tritoanst/ccxt,thijstriemstra/ccxt,tritoanst/ccxt,aiueogawa/ccxt,thijstriemstra/ccxt,aiueogawa/ccxt,aiueogawa/ccxt,tritoanst/ccxt,ccxt/ccxt,tritoanst/ccxt,thijstriemstra/ccxt,thijstriemstra/ccxt,aiueogawa/ccxt,ccxt/ccxt,ccxt/ccxt,ccxt/ccxt,ccxt/ccxt