[Bug] UrlBuilder cuts off trailing slash

[mrSkyven]

Need to send some Post request to the Url like
http://foo.com/baz/
When using SendBuilder.AppendPath trailing slash is missing in result Url, which causes 405
Example:

var urlBuilder = new FluentRest.UrlBuilder("http://foo.com/");
urlBuilder.AppendPath("/baz/");
var url = urlBuilder.ToString();

Result
http://foo.com/baz