update to libav dff1c19140e70

This includes patch 0c0825659 which fixes the ASF seeking bug.

Closes #16
add changelog file
build: use GNUInstallDirs
Release 3.0.5
build: avoid useless dependencies
Release 3.0.6
fix cmake build warnings
use ebur128 true peak instead of sample peak
add installation note for Debian
only use AV_DICT_IGNORE_SUFFIX when listing all entries

fixes a bug where accessing "album" metadata would instead
return the "album_artist".
update to libav afdf946
use the compand filter to allow setting the gain to > 1.0

closes #45
log error when cannot set up filter graph
loudness: fix crash for songs with 0 frames. closes #48
playlist example: fix race condition
Release 3.0.7
fix memory corruption when replaygain scanning large album
update to libav 10.0
playlist: fix segfault on out of memory
playlist: fix segfault race condition when adding a sink