Readding fromJSON data coercion in recordResponse.

[Pull Request #486](https://github.com/spine/spine/pull/486/files) removed `data = @model.fromJSON(data)` from `recordResponse` which caused [Issue 504](https://github.com/spine/spine/issues/504).

This Pull Request resolves [Issue 504](https://github.com/spine/spine/issues/504) for people with custom APIs that need `fromJSON` to process their models before loading their data.