version mismatch error disobeys --json

If the version in .flowconfig doesn't match the version being run, you get an error:

```
$ flow status ~/playground
Launching Flow server for /data/users/mroch/playground
Wrong version of Flow. The config specifies version ^0.46.0 but this is version 0.47.0
Could not start Flow server!
```

Passing `--json` doesn't return JSON. this is bad for any integration expecting JSON, like https://github.com/flowtype/flow-for-vscode/issues/72