Changed the version number to 2.3.0.

git-svn-id: https://plugins.svn.wordpress.org/fetch-tweets/trunk@905884 b8457f37-d9ea-0310-8a92-e5e31aec5664
Marked 2.3.0 as stable.

git-svn-id: https://plugins.svn.wordpress.org/fetch-tweets/trunk@905888 b8457f37-d9ea-0310-8a92-e5e31aec5664