Asphalt

- Fixed memory leak when ``stream_events()`` is called but the returned generator is never used

- Fixed incompatibility with Python 3.5.2

- Removed the requirement for async generators to yield at least once when wrapped with
``context_teardown``
- Removed aiogevent support since it has been removed from PyPI

- The runner now calls ``logging.shutdown()`` after the event loop has been closed
- Added the ``Context.get_resources()`` method
- Made ``stream_events()`` connect to the signal when called instead of the first iteration of the
async generator

- Allowed selecting the service to run with ``asphalt run`` using an environment variable
(``ASPHALT_SERVICE``)

- Added support for the `Tokio <https://github.com/PyO3/tokio>`_ event loop
- Added a feature to the runner that lets one define multiple services in a configuration file and
select which one to run
- Increased the runner default start timeout to 10 seconds