function property(key) {
      key = String(key);
      return function(object) {
        return object == null ? undefined : object[key];
      };
    }
Creates a "_.pluck" style function which returns the property value
of `key` on a given object.

@static
@memberOf _
@category Utility
@param {string} key The name of the property to retrieve.
@returns {Function} Returns the new function.
@example

var users = [
  { 'user': 'fred',   'age': 40 },
  { 'user': 'barney', 'age': 36 }
];

var getName = _.property('user');

_.map(users, getName);
// => ['fred', barney']

_.pluck(_.sortBy(users, getName), 'user');
// => ['barney', 'fred']