Add asyncio aiohttp transport for raven-python

[asvetlov]

The transport sends sentry messages asynchronously in separate asyncio task.
But it requires started asyncio event loop.
Works on Python 3.3+
Dependencies: tulip (for Python 3.3) and aiohttp library.

[asvetlov]

I see some errors on Travis like

=================================== FAILURES  ===================================
_______________________ DjangoClientTest.test_user_info ________________________
tests/contrib/django/tests.py:189: in test_user_info
>       assert 'user' in event
E       AssertionError: assert 'user' in {'culprit': 'tests.contrib.django.views in raise_exc', 'event_id': '0326a3d8026044399a23c21af2403122', 'exception': {'...ravis/virtualenv/pypy-2.2.1/bin/py.test'", "'tests/'", "'--cov'", "'raven'", "'--cov-report'", "'term-missing'")}, ...}

But the errors definitely are not related to my changes

[asvetlov]

@dcramer would you like to include asyncio/aiohttp transport into raven?
I've tested it locally and the code works good.
This week I'll start to use aiohttp transport in our products btw.

[dcramer]

the comment about tornado is wrong, right?

[asvetlov]

Fixed

[asvetlov]

@dcramer I've fixed the doc and added more verbose response error handling.
Also now aiohttp transport supports HTTP keepalives. Does sentry server process it?

Also please describe what should I do with AioHttpTransport? What code is obsolete?

[asvetlov]

@dcramer I've fixed all your notes.

[dcramer]

Thanks!

[asvetlov]

Thank you too!

[asvetlov]

@dcramer when do you want to publish release with aiohttp transport?

[popravich]

@asvetlov, there is a typo -- aiohttp.TCPConnector missing loop argument.

Also family argument in __init__ never used.

[asvetlov]

@popravich see #480

[popravich]

Looks good