update compatible version.

git-svn-id: http://plugins.svn.wordpress.org/featured-image-via-url/trunk@826980 b8457f37-d9ea-0310-8a92-e5e31aec5664
set stable tag to trunk.
Merge branch 'master' of github.com:tsaiid/wp-plugin-featured-image-via-url

Conflicts:
	readme.txt