Highlight path head and tail differently.

I'm not sure this is the right way to do this, so what I really wanted was some comments. Can the source hooks be overriden? I couldn't find info about this in the documentation.

IMHO, this change might help find files visually in the MRU list. See, for example,
![captura de pantalla de 2014-07-13 15 46 55](https://cloud.githubusercontent.com/assets/221465/3565657/4553ad48-0ac7-11e4-84f4-922a696cb811.png)