Don't clobber `in` and `name` fields in body/form parameters

Fixes #2.  I'll try to follow this up with a corresponding test script.
I think that the description below from [Parameter Object fixed fields][0] means that you actually need a *parameter* and not a schema for the whole body. I will ask @swagger-api about it.

> parameter" from "Required. The schema defining the type used for the body parameter

[0]: https://github.com/swagger-api/swagger-spec/blob/master/versions/2.0.md#fixed-fields-7