added docstring for Item.create(initial_products) (#91)

Author: zevaverbach

plaid/api/item.py

@@ -134,6 +134,8 @@ def create(self,
                                                         ``password``, and
                                                         (optionally) ``pin``.
         :param  str     institution_id:
+        :param  list    initial_products:               A list containing 
+                                                        product names.
         :param  str     transactions__start_date:       The date to begin the
                                                         item's initial
                                                         transaction pull.