update installation instructions and FAQ on how to generate API key


git-svn-id: https://plugins.svn.wordpress.org/g-crossposting/trunk@771107 b8457f37-d9ea-0310-8a92-e5e31aec5664
tested and confirmed compatibility with Wordpress 3.6.1


git-svn-id: https://plugins.svn.wordpress.org/g-crossposting/trunk@771108 b8457f37-d9ea-0310-8a92-e5e31aec5664