fixed yahoo client error: use https instead of http

This change should fix the Yahoo Client Error described below.

For Yahoo Authentication, the API now requires HTTPS. Please refer to the discussion on the page (https://developer.yahoo.com/forum/OAuth-General-Discussion-YDN-SDKs/http-social-yahooapis-com-Will-be-right-back/1395509802423-89faffa2-1503-486d-bc29-6505719bd774) and the comment from "africa356" on Mar 24, 2014.