Added support for Starling Bank

[dullage]

Description:

Added support for Starling Bank.

Pull request in home-assistant.github.io with documentation (if applicable): home-assistant/home-assistant.io#6236

Example entry for configuration.yaml (if applicable):

sensor:
  - platform: starlingbank
    accounts:
      - name: "Spending Money"
        sandbox: false
        access_token: YOUR_PERSONAL_ACCESS_TOKEN
        balance_types:
          - 'cleared_balance'
          - 'effective_balance'

Checklist:

• The code change is tested and works locally.
• Local tests pass with tox. Your PR cannot be merged unless tests pass

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.github.io

If the code communicates with devices, web services, or third-party tools:

• New dependencies have been added to the REQUIREMENTS variable (example).
• New dependencies are only imported inside functions that use them (example).
• New or updated dependencies have been added to requirements_all.txt by running script/gen_requirements_all.py.
• New files were added to .coveragerc.

If the code does not interact with devices:

• Tests have been added to verify that the new code works.

[homeassistant]

Hi @dullage,

It seems you haven't yet signed a CLA. Please do so here.

Once you do that we will be able to review and accept this pull request.

Thanks!

[MartinHjelmare]

We have renamed add_devices to add_entities.

[dullage]

Thanks @MartinHjelmare, I think I'm write in saying this is just a cosmetic thing? If so, would it be a good idea for me to wrap this rename up in a bigger change at a later date?

[MartinHjelmare]

Yes, nothing is broken like this. 👍

But it's nice to keep everything in sync to allow future smooth migrations.