Updated to version 0.8.3 (Also stable tag)

git-svn-id: https://plugins.svn.wordpress.org/bitbucket-issue-manager/trunk@863294 b8457f37-d9ea-0310-8a92-e5e31aec5664
Updated readme.txt

git-svn-id: https://plugins.svn.wordpress.org/bitbucket-issue-manager/trunk@863296 b8457f37-d9ea-0310-8a92-e5e31aec5664