Added initial localization support.

git-svn-id: https://plugins.svn.wordpress.org/twitter-tags/trunk@847156 b8457f37-d9ea-0310-8a92-e5e31aec5664
Updated readme.txt to set 1.2.1 as stable

git-svn-id: https://plugins.svn.wordpress.org/twitter-tags/trunk@847157 b8457f37-d9ea-0310-8a92-e5e31aec5664