Automark: first release

Simple plugin that automatically highlights current word (no hotkeys or so on):

![Automark](http://i.imgur.com/q6YyuN4.png)

Now I should touch 16 files, right? (remembered that magic number)
OK, good, it's explained :)
Anyway again, don't feel obligated to change anything, I was just pointing this out after your comment on `plugin_idle_add()` missing the destroy notify; just use the method you like the most as they are equivalent anyway.