updated docs

git-svn-id: https://plugins.svn.wordpress.org/landing-pages-builder/trunk@1010958 b8457f37-d9ea-0310-8a92-e5e31aec5664
Updated docs (fixed minor typo)

git-svn-id: https://plugins.svn.wordpress.org/landing-pages-builder/trunk@1010965 b8457f37-d9ea-0310-8a92-e5e31aec5664