Aiostream

- Better error handling in user code (PR 47)
- More links and details in the doc (PR 50, thanks blaiseli )
- Better exception when a stream is used as a context (issue 40, PR 56)
- Better exceptions in AsyncIteratorContext (PR 57)
- Fix python 3.8 compatibility (PR 59, issue 61, PR 62)

- Implement [call](https://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.call) operator (PR 43)
- Enhance [list](https://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.list) operator (PR 44)
- Add [until](https://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.until) operator (PR 45)

- Set encoding to utf-8 in setup script (PR 42)

- PR 24: Raise a better exception when decorating a method with operator
- PR 27: Fixed deprecation warning for importing ABC's from collections
- PR 32: Refactor `base_combine` and the streamer manager
- PR 33: `AsyncIteratorContext` now re-throws exceptions within the iterator
- PR 34: Use `AsyncExitStack` from contextlib

- PR 19: Add python 3.7 support
- Issue 20, PR 21: Add [await_](http://aiostream.readthedocs.io/en/latest/utilities.html#aiostream.aiter_utils.await_) and [async_](http://aiostream.readthedocs.io/en/latest/utilities.html#aiostream.aiter_utils.async_) helper functions
- Issue 14, PR 22: Add [ziplatest](http://aiostream.readthedocs.io/en/latest/operators.html#aiostream.stream.ziplatest) operator

- PR 10: add concurrency to `map` and `starmap` operators
* `ordered` argument can be used to get the elements either in order or as soon as possible.
* `task_limit` can be used to limit the amount of mapping coroutines that can run concurrently.