Embedded field and promoted methods stubbed incorrectly

I ran depstubber using the following comment
```
//go:generate depstubber -vendor github.com/revel/revel Controller,Params
```
The stub generated for Params is wrong in several ways: the embedded field of type `url.Values` has been given the name `Values`; various methods, like `Get`, which are methods on `url.Values` have been created as methods on `Params`.

I have attached the generated stub. I had to change the extension to make that work.
[stub.go.txt](https://github.com/github/depstubber/files/5225603/stub.go.txt)