Update pianobar to 2017.08.30

Summary:

• Support binding to specific network interface, see config option bind_to
• New config option gain_mul softens effect of replay gain
• Replaced deprecated ffmpeg and json-c functions, bumps ffmpeg/libav version requirement
• Fix use-after-free
• Minor improvements to code and documentation

Signed-off-by: Pierre-Yves <pyu@riseup.net>

Test Plan: Can run the application but the service is only available in the U.S.

Reviewers: Triage Team

Differential Revision: https://dev.solus-project.com/D1933