Incompatible with aiohttp>=3.6

[ibt23sec5]

Hello,
elasticsearch_async is no more compatible with aiohttp, since version 3.6 due to dropping of explicit parameter loop:

Traceback (most recent call last):
  ... 
    self.client = elasticsearch_async.AsyncElasticsearch(hosts=es_addresses)
  File "/home/ibt23sec5/projects/urpp/venv/lib/python3.7/site-packages/elasticsearch_async-6.2.0-py3.7.egg/elasticsearch_async/__init__.py", line 8, in __init__
    super().__init__(hosts, transport_class=transport_class, **kwargs)
  File "/home/ibt23sec5/projects/urpp/venv/lib/python3.7/site-packages/elasticsearch-7.5.1-py3.7.egg/elasticsearch/client/__init__.py", line 227, in __init__
    self.transport = transport_class(_normalize_hosts(hosts), **kwargs)
  File "/home/ibt23sec5/projects/urpp/venv/lib/python3.7/site-packages/elasticsearch_async-6.2.0-py3.7.egg/elasticsearch_async/transport.py", line 23, in __init__
    connection_pool_class=connection_pool_class, **kwargs)
  File "/home/ibt23sec5/projects/urpp/venv/lib/python3.7/site-packages/elasticsearch-7.5.1-py3.7.egg/elasticsearch/transport.py", line 129, in __init__
    self.set_connections(hosts)
  File "/home/ibt23sec5/projects/urpp/venv/lib/python3.7/site-packages/elasticsearch_async-6.2.0-py3.7.egg/elasticsearch_async/transport.py", line 56, in set_connections
    super().set_connections(hosts)
  File "/home/ibt23sec5/projects/urpp/venv/lib/python3.7/site-packages/elasticsearch-7.5.1-py3.7.egg/elasticsearch/transport.py", line 179, in set_connections
    connections = list(zip(connections, hosts))
  File "/home/ibt23sec5/projects/urpp/venv/lib/python3.7/site-packages/elasticsearch-7.5.1-py3.7.egg/elasticsearch/transport.py", line 175, in _create_connection
    return self.connection_class(**kwargs)
  File "/home/ibt23sec5/projects/urpp/venv/lib/python3.7/site-packages/elasticsearch_async-6.2.0-py3.7.egg/elasticsearch_async/connection.py", line 73, in __init__
    ssl_context=ssl_context,
TypeError: __init__() got an unexpected keyword argument 'loop'

[sethmlarson]

This is being tracked here: https://github.com/elastic/elasticsearch-py/issues/1332
See #81 for more information.