Almost fully-functional Mavericks version
General Notes
This recovers a lot of the plugin's functionality from Mountain Lion. Mail.app changes caused keyboard shortcuts in the messages/preview pane to fail. I've since migrated a lot of the implementation to using Mail APIs, which means that older versions of OS X may fail to function. You should still be able to grab an older binary from the repository's history, though.
As always, I'll do my best to respond to bugs and pull requests!
Known Issues
- h/j navigation in the messages view still doesn't work properly - there's an existing bug with the implementation of the Mail.app API, and left/right keys don't seem to trigger keyDown for some reason