be abble to send a json response with a 404 handler 

use case rest api:
 be abble to send a json response without to create a template, shorcut the rendering.

```
route file:
 {404, [{controller, "v1"}, {action, "not_found"}]}.
```

```erlang
not_found('GET', _) ->
    {404, jsx:encode([{error, <<"Invalid Request">>}]), [{"Content-type","application/json"}]}.
```
Merge pull request #506 from mihawk/patch-19

be abble to send a json response with a 404 handler