get_the_excerpt support and other general improvements

git-svn-id: https://plugins.svn.wordpress.org/smart-search/trunk@971510 b8457f37-d9ea-0310-8a92-e5e31aec5664
forgot to add stable tag

git-svn-id: https://plugins.svn.wordpress.org/smart-search/trunk@971512 b8457f37-d9ea-0310-8a92-e5e31aec5664