Adding Spanish language files

git-svn-id: https://plugins.svn.wordpress.org/lightweight-social-sharing-buttons/trunk@967260 b8457f37-d9ea-0310-8a92-e5e31aec5664
updating readme.txt and main php

git-svn-id: https://plugins.svn.wordpress.org/lightweight-social-sharing-buttons/trunk@967262 b8457f37-d9ea-0310-8a92-e5e31aec5664