Support for ESM format
Support for ESM format

With this modification, you can pick the format that suits you better between ESM, AMD and CJS (default) in the config:

```js
meta: {
    "*.hbs": {
      "defaultExtension": false,
      "format": "esm",
      "loader": "hbs"
    }
}
```

I resorted to this modification because the hardcoded CJS style translation didn't get along well with rollup static optimization when using `jspm build`.

tabs to spaces

indentation

davis/plugin-hbs,davis/plugin-hbs