Inconsistent documentation for Client

[alexanderkjeldaas]

The above haddock says that the reader should ignore the RunClient typeclass, and the associated Client type (since it's undocumented).

However, lots of functions return Client which means the user cannot ignore understanding what it is.

The documentation should be updated.

[alpmestan]

Hmm, indeed, This sentence doesn't really help anyway, we should replace it with a description of at least the Client type family and a few words about clientWithRoute.