Fix internal IntegrationTests

[hallucinogen]

Our internal integration tests was broken. This will fix it.

For the case of HttpClient, we can't do OnSuccess. If you take a look inside the code, we do special handling on error.

[richardjrossiii]

Personally, I dislike this idea of doing it this way, because this requires that either:

1. HostName ends with a /
2. or relativeUri begins with a /

But never both. It works, I'm just afraid of something weird happening here as we move toward 'HostName' being more public.

[hallucinogen]

It works if both have /. I've tested this. But if none have /, it breaks.

The only issue I have with doing new Uri(ParseClient.HostName, relativeUri); is that

new Uri("https://api.parse.com/1/", "gogo");

translates into

https://api.parse.com/gogo

and not

https://api.parse.com/1/gogo

I'm open to better solution.

[richardjrossiii]

I swore the issue was that

new Uri(new Uri("https://api.parse.com/1/"), "/gogo")

resulted in

https://api.parse.com/gogo

Unless I'm reading the Docs wrong...

As long as all of our relativeUris don't have leading slashes (which I thought I got rid of in #77), we should keep the path part of the HostName.

[hallucinogen]

That makes sense! Let me double-check and update this PR