Depend on either jQuery or Underscore

Even though we already did that for the Deferred(), we used _.map and _.each
through the code. Fixed that to use either _.map or $.map.

@rgrp Is this repository is still relevant, or recline uses something else? It would be very useful to have a kind of ```ckan.js``` API, unrelated to Recline, and this is a great starting point IMO.