Feature/segments options

`segments_options` support for codem-transcode.
Support of these options is added by
https://github.com/madebyhiro/codem-transcode/pull/33/files

`segments_options` stores valid JSON string just like `thumbnail_options`.
So far the only valid option is `segment_time`.

```ruby
{ "segment_time": 10 }
```

Also /api/jobs/:id.json now shows thumbnails, playlist and segments returned from
the transcoder.

This code also includes "wrap_parameters" fix. #29