Support for JSON API default encoding application/vnd.api+json

[andreas83]

If the encoding is set to "application/vnd.api+json" which is used by
JSON API, the response is not proper formatted:
Response:
[object Object]

Should be quite easy to support application/vnd.api+json as encoding too

[netojose]

Thanks for your feedback, @andreas83 , I will look this friday (feb/8/2019)