function propertyOf(object) {
	      return function(key) {
	        return object == null ? undefined : object[key];
	      };
	    }
The inverse of `_.property`; this method creates a function which returns
the property value of a given key on `object`.

@static
@memberOf _
@category Utility
@param {Object} object The object to inspect.
@returns {Function} Returns the new function.
@example

var object = { 'user': 'fred', 'age': 40, 'active': true };
_.map(['active', 'user'], _.propertyOf(object));
// => [true, 'fred']

var object = { 'a': 3, 'b': 1, 'c': 2 };
_.sortBy(['a', 'b', 'c'], _.propertyOf(object));
// => ['b', 'c', 'a']