Does not handle file Parameters

[spaceraccoon]

As per the OpenAPI v2 documentation, If type is "file", the [consumes](https://swagger.io/specification/v2/#operationConsumes) MUST be either "multipart/form-data", " application/x-www-form-urlencoded" or both and the parameter MUST be [in](https://swagger.io/specification/v2/#parameterIn) "formData".

Currently, grape-swagger processes file parameters normally and does not enforce these requirements, leading to invalid OpenAPI v2 output.