Automark: first release

Simple plugin that highlights current word:

![Automark](http://i.imgur.com/q6YyuN4.png)

Now I should touch 16 files, right? (remembered that magick number)
You need to unregister the source in plugin_cleanup() to avoid crashes.  Alternatively you can use plugin_timeout_add() which deals with it automatically -- but if you want to manage your source manually anyway manual removal is fine.