Recommendations client

[Casao]

Adds new client to return User and Job recommendations in a hash with the recid (and other metadata). We need this RecID field to start doing NDCG on recs calls.

Done side by side with existing code (which is in the poorly name Recommendation class) for a transition and to avoid the major version bump.

[Casao]

CC is for identical code (this started as a copy paste code). The old code will eventually be removed, so I don't see any point in changing this code to appease the CC gods, and I don't see any value in refactoring to make these private methods available to both.

[tkling]

:thumbsup: LGTM. I dig the side-by-siding to avoid the major bump for now!

[Casao]

@tkling updated with Map, and added spec for single hash result (since i didn't get what the stupid [].flatten was doing at first and nearly removed it)

[tkling]

@Casao :thumbsup: :thumbsup: mergin'