Enable compression

This PR doesn't actually **do** anything.

**1)** To enable compression, we should add the following Heroku config:

```bash
heroku config:add ASSET_SYNC_GZIP_COMPRESSION=true
```

This configuration will tell AssetSync to upload the gzipped version to S3 and ignore the uncompressed one.

**2)** In this PR there's also a minor change (remove some whitespaces) to change the JS file SHA hash and thus trigger new asset sync (to sync the compressed file)