Upgrade py-cpuinfo to 3.0.0

[fabaff]

3.0.0

• Change API to hide low level functions
• Combine data from all sources instead of picking one
• Not working on OS X 10.12 Sierra
• Change version number format
• Not working on ARM64 odroid-c2

Tested with the following configuration:

sensor:
  - platform: cpuspeed
    name: CPU

[mention-bot]

@fabaff, thanks for your PR! By analyzing the history of the files in this pull request, we identified @balloob, @rmkraus and @robbiet480 to be potential reviewers.