Deprecate Gets in favor of MultiGets

[bryankane]

As discussed with @saeta and @josh-newman -- gets are basically just a MultiGet of one id, so it doesn't make sense to write both Gets and MultiGets. We should add support to Naptime to convert a get to a multiGet of one element, and deprecate gets going forward. Developers will then be able to only write a multiget, and get support for both gets and multiget.