Update ListError.cs

The API error response wasn't de-serialising email and error message correctly. From the API docs:
    "errors": [
        {
            "email": {
                "email": "example email",
                "euid": "example euid",
                "leid": "example leid"
            },
            "code": 42,
            "error": "example error",
            "row": {
                "...": "..."
            }
        }
Merge pull request #58 from paulandrewcampbell/master

Update ListError.cs