- Warn about setting parser at the top level. Refs. #4638.
- Remove top level parser from examples. Instead show the most common
options (I also removed printWidth, since we don't recommend changing
it). Refs. #4638.
- Show how to configure the flow parser for .js files. Refs. #4638.
- Update valid options for the parser option, including links and "since
version".
- Clarify babylon vs flow.