Homekit

Fixes:
- Travis builds fail for OS X
- Zeroconf fails during unregistering non existing device

Improvements:
- Adds travis build for Python 3.8

This release adds the following improvements:
* add option to use file as input for put_characteristic
* improve handling of closed connections
* Ignore unsupported pairings without failure

Bugfixes:
* Fix 189 get accessories fails for ble
* Fix 188 remove_pairing uses wrong content-type

This release adds the following improvements:
- Implement a debug proxy, see [the documentation](./doc/DebugProxy.md) for more information.
- Add support for Windows including automated tests on travis.ci
- Add support for [plugins](./doc/Plugins.md) to support decoding of non-standard tlv8 characteristics

Bugfixes:
- fix a bug in homekit/accessoryserver.py where the wrong variable was used in the error message
- add tlv8 to the list of install requirements in setup.py
- Fix decoder for supported audio configuration
- add decoder for supported-rtp-configuration characteristic

This release adds the following improvements:
* introduces device reports for working accessories
* power on bluetooth adapter if required and restore power state after usage
* add filter for the discovery commands to show only unpaired devices
* implement adding additional pairings to accessories

This release adds the following improvements:
- add check for valid structure of accessory pin (XXX-XX-XXX)
- implement 2 stage pairing: support accessories with generated accessory
pins
- clean up get_characteristics parameters to work with tado internet bridges
- add host header on HomeKit IP requests to work with tado internet bridges
- skip Accept-Encoding header when pairing IP accessories also for to work
with tado internet bridges
- HomeAssistent already has discovery via zeroconf. We support this by
extracting a function for parsing the HomeKit specific data

This release adds basic Bluetooth LE support.