Python 3.7 firebase async sorunu

lol. I 'fix' this 'issue' that is long than an year.

1. you should rename file async.py ( i choose async_fb.py)
2. then in 'init.py' file replace line 3 with: from .async_fb import process_pool
3. then in 'firebase.py' file replace line 12 with: from .async_fb import process_pool
   this is embarrassing...
   Enjoy codding!