Update pianobar to 2014.06.08

Additionally, the `head` block isn't needed because both HEAD and 20140.06.08 use pkg-config.
It appears to be a hard dependency now — see
- [src/player.c](https://github.com/PromyLOPh/pianobar/blob/2014.06.08/src/player.c#L34-L66)
- [Makefile](https://github.com/PromyLOPh/pianobar/blob/2014.06.08/Makefile#L76-L94)