In situations when the client fails with certain error codes,
it should be able to retry the request. Ideally, it would
retry the request to a different host so that in the event that
an instance malfunctioned or was removed, the request wasn't
consistently failing.

In particular, make retry more configurable by allowing the user to set
the number of attempts and the strategy to determine whether a response
should be retried. Also explicitly disabled retries on the request, so
that it would be entirely handled within the Guava retryer. The reason
that retries within the HttpClient can't be re-used is that doing so
would just retry the given HttpRequest, and this needs to be able to
alter the HttpRequest between attempts. Also is a little more careful
about retrying to different hosts on requests.

I was doing something that looked like
```
url = hostToUrl(host)
actualUrl = hostToUrl(url)
```
which was very obviously wrong. This fixes it so that
it only builds the URL once, which is the correct
write way to do this.