clarifies instructions in proxy challenge 

Also added a wikipedia link for complete beginners to read up on proxies and hapi's reply.proxy() ref.
Let me know if this is too much. Thanks.

I like the first part of the sentence, "A proxy lets you relay requests from one one server/service to another". I'd say we should cut the part after that. I'm not sure we want to explain the reasons why a proxy is useful because there are so many.