* Add `--help` CLI flag
* Don't pick up unknown CLI options
This prevents people from adding new CLI options in the future, but
forgetting to add it explicitly to minimist, resulting in a false
"Ignored unknown option" warning.
* Add `-h` and `-v` option aliases
It always bugs me when those don't do `--help` and `--version` for no
reason in CLIs.
* Allow `echo 'test' | prettier` without the `--stdin` flag
* Improve CLI error handling and validation
- Handle errors the same way both when using stdin and when using files.
- Print validation errors nicely.
- Validate int options, instead of silently ignoring bad input.
- Warn about unknown parsers, falling back to babylon. If a new parser
is added in the future, this allows graceful degradation for tools
running an older version of prettier. (Just like how unknown options
are warnings instead of errors.)
- Add comments.
* Run prettier on bin/prettier.js