Upgrade to bluepy 1.2.0

Merge pull request #14 from brianpeiris/upgrade-bluepy

Upgrade bluepy and fix service uuid ordering

Errors for humans

• Improve error messages.

New beginnings

• Ditched support for older firmware. The code is much cleaner now.
• status command is cheap now -- it just reads the switch state from the advertised data instead of connecting to and reading from the device.
• status command now takes a mac_address before the command, to match the other commands.
• Added a toggle command.
• Added a battery-level command.

Support for old and new firmware

Use this version if you still need support for the old firmware -- the one that required an auth key.