added python3-attrs are dependancy
added python3-attrs are dependancy

Note the import is 'attr', but the package in pypi is 'attrs'. 
--
 File "/usr/lib/python3.5/site-packages/aiohttp/__init__.py", line 6, in <module>
    from .client import *  # noqa
  File "/usr/lib/python3.5/site-packages/aiohttp/client.py", line 16, in <module>
    from . import client_exceptions, client_reqrep
  File "/usr/lib/python3.5/site-packages/aiohttp/client_reqrep.py", line 13, in <module>
    import attr
ImportError: No module named 'attr'
bachp/meta-homeassistant,bachp/meta-homeassistant,bachp/meta-homeassistant