Don't try to connect to Tumblr if we don't have an API connection.

git-svn-id: https://plugins.svn.wordpress.org/tumblr-crosspostr/trunk@853946 b8457f37-d9ea-0310-8a92-e5e31aec5664
Register post formats support ourselves, version bump to 0.5.

git-svn-id: https://plugins.svn.wordpress.org/tumblr-crosspostr/trunk@853947 b8457f37-d9ea-0310-8a92-e5e31aec5664