Changed the version number.

git-svn-id: https://plugins.svn.wordpress.org/fetch-tweets/trunk@901363 b8457f37-d9ea-0310-8a92-e5e31aec5664
Marked 2.2.0 as stable.

git-svn-id: https://plugins.svn.wordpress.org/fetch-tweets/trunk@901366 b8457f37-d9ea-0310-8a92-e5e31aec5664