SUPPORT for ActionController::Parameters

If parameters are not sent as a raw json string, but rather in a
FormData object, the object to parse will look like:

```
{
  "id" => "1",
  "array" => {
    "0" => "foo",
    "1" => "bar"
  }
}
```

Fix parsing of this by extracting the values of the hash.
Merge pull request #2 from MaximeD/support-for-parameters

SUPPORT for ActionController::Parameters