Aiohomekit

This release reverts 01069fc6f5114e96275809e2128c27aa1d62b872 as it was causing issues for some of our Home Assistant users with real certified devices.

It also:

* Adds a bunch more TLV structs for dealing with HomeKit cameras
* Improves the aiohomekit command line tool (aiohomekitctl)
* Removed some code that wasn't called
* Changed the order of the headers we said to match what an iOS client does. This fixes a compatibility issue with Heatmiser Neohub.
* Makes our state handling during pairing and when establishing a secure connection more tolerant of bad devices. This fixes compatibility with Heatmiser Neohub.

Process wise we:

* Improved our CI and how it sends coverages reports to codecov
* Bumped the version of a bunch of our linters

With 0.2.51 we have stopped using travis for CI and moved to GitHub Actions. This means we have Windows and macOS test runs for python 3.7 and 3.8.

In addition:

There is a new TLVStruct mixin in `aiohomekit.tlv8` that can be used with structs like `StreamingStatus`, e.g.:

python
from dataclasses import dataclass

from aiohomekit.tlv8 import TLVStruct, tlv_entry
from aiohomekit.model.characteristics.const import StreamingStatusValues

dataclass
class StreamingStatus(TLVStruct):
status: StreamingStatusValues = tlv_entry(1)


A raw characteristic can be decoded using`StreamingStatus.decode(b'\x01\x02\x01')`.

This works with the IntEnum's we define in `aiohomekit.model.characteristics.const`.

There is now an async `image()` method on a pairing that can be used to take a snapshot of a HomeKit camera. The params are the aid, width and height. It returns a JPEG as `bytes`.

- Adds a licence file to make life easier for distro packagers

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