AIOHttpConnection init raises AttributeError on use_ssl with Elasticsearch>2.0.0

[artemknd]

aioelasticsearch==0.5.2
elasticsearch==2.4.1

AIOHttpConnection takes use_ssl argument and passes one to the parent's __init__.

Then self.use_ssl gets used instead of use_ssl here
https://github.com/aio-libs/aioelasticsearch/blob/master/aioelasticsearch/connection.py#L52

It works for the latest elasticsearch-py versions, however, it doesn't work with >2.0.0, b/c there's no self.use_ssl = use_ssl there.

The fix is straightforward - use use_ssl directly instead of self.use_ssl.