Adding banner to plugin root, This should probably be moved to Assets in the neat future.

git-svn-id: https://plugins.svn.wordpress.org/compatible-post-sharing-system/trunk@931106 b8457f37-d9ea-0310-8a92-e5e31aec5664
Moving banner and screenshots to assets.

git-svn-id: https://plugins.svn.wordpress.org/compatible-post-sharing-system/trunk@931110 b8457f37-d9ea-0310-8a92-e5e31aec5664