* move is_off property to SmartDevice, implement is_on for bulb and use it
* refactor by moving smartbulb and smartplug to their own classes
* drop python2 compatibility, make flake8 happy
* travis: remove 2.7, add 3.6
* Add support for new-style protocol
Newer devices (including my LB130) seem to include the request length in
the previously empty message header, and ignore requests that lack it. They
also don't send an empty packet as the final part of a response, which can
lead to hangs. Add support for this, with luck not breaking existing devices
in the process.
* Fix tests
We now include the request length in the encrypted packet header, so strip
the header rather than assuming that it's just zeroes.
* Create a SmartDevice parent class
Add a generic SmartDevice class that SmartPlug can inherit from, in
preparation for adding support for other device types.
* Add support for TP-Link smartbulbs
These bulbs use the same protocol as the smart plugs, but have additional
commands for controlling bulb-specific features. In addition, the bulbs
have their emeter under a different target and return responses that
include the energy unit in the key names.
* Add tests for bulbs
Not entirely comprehensive, but has pretty much the same level of testing
as plugs
