[Fixed] take the left margin into calculation

- Now available for themes with non-zero left margin sidebars

git-svn-id: https://plugins.svn.wordpress.org/standard-widget-extensions/trunk@798959 b8457f37-d9ea-0310-8a92-e5e31aec5664
Release 1.3

- using a useful function offsetParent() and other refactoring
- Japanese resource
- readme.txt updated

git-svn-id: https://plugins.svn.wordpress.org/standard-widget-extensions/trunk@798960 b8457f37-d9ea-0310-8a92-e5e31aec5664