Force visual display of "Send this post to Tumblr?" legend.

git-svn-id: https://plugins.svn.wordpress.org/tumblr-crosspostr/trunk@875548 b8457f37-d9ea-0310-8a92-e5e31aec5664
Add human readable error messages and when crossposting fails.

git-svn-id: https://plugins.svn.wordpress.org/tumblr-crosspostr/trunk@875549 b8457f37-d9ea-0310-8a92-e5e31aec5664
Update `.pot` file, readme, version bump to 0.7.8.3.

git-svn-id: https://plugins.svn.wordpress.org/tumblr-crosspostr/trunk@875550 b8457f37-d9ea-0310-8a92-e5e31aec5664