* Use f-strings instead of .format()
* Code block language marker fixes
* Make example code blocks syntactically valid Python
* Run all python code blocks through black
https://github.com/scop/misc/blob/master/black_markdown.py
* Add some missing code block language markers
* Use shell language consistently to mark shell code blocks
* Undo folding of some example dicts
* Remove outdated OrderedDict comments per Python 3.7, replace with plain dict
* Improve frontend development setup instructions
- Currently you recommend cloning the `home-assistant-polymer` repository directly. I assume you should instruct people to fork it, like you do in the [development environment documentation](https://developers.home-assistant.io/docs/en/development_environment.html)
- I had some trouble setting `development_repo` in macOS, I believe a trailing slash was necessary in the path. Have updated to a realistic macOS example path
* Link to Getting Started instead of macOS install instructions
* Revert comment change
* Change link to Installation Guide
* Adjust link to point to dev setup docs
