Generate classes from the models declared in 'responseModel'

* ResponseMessage has new constructor parameter, an optional string for responseModel
* Make sure we add it to list of models
* make sure the responseModel is part of the error list available to mustache
allow list of models to be returned in errors

* for example, a list of validation errors with an exceptional status
Update java mustache to show error status codes and models in generated API, in comments.

* I wonder if there is some clever way to make exceptions based on the model thrown, and automatically fill them in with the parsed error models?
* Until then, it's comments, and roll your own.
Regenerate sample java files with example response status codes

* none of existing examples use the responseMessage.responseModel feature, but I have tested it.
* Didn't want to muck with sample json
* update the scripts used to generate both java versions.
* see https://github.com/wordnik/swagger-spec/blob/master/versions/1.2.md#525-response-message-object
Merge pull request #206 from xoom/issue/modelsFromStatus

Issue/models from status - utilize the responseModel, if present