Remove model name from nickname, swagger spec understands op context.

This removes the redundancy from paths in swagger-ui such as
`/api/user/user_login`. It will now be displayed simply as
`/api/user/login`.

This is consistent with how `nickname` is used in Swagger examples.
If I understand you correctly, you are saying that your version shortens `foo.bar.baz` to `bar.baz`, while mine shortens to `baz`, is that correct? In that case, `/^[^.]*\./` works as requested.

Anyways, let's not be too picky about the regex. Please add enough unit test cases to make it clear what is the expected behaviour for different input. The regex can remain an implementation detail that way.