Update audio/soundkonverter to 2.0.91.

Changes:

• Add cdrkit as an optional ripper dependency
• Switch to using Github (old source no longer updated)

Changelog:

new in 2.0.91 (2.1.0 rc2):
-Add: Full GUI support for album artist tags

including the CD ripper

-Add: Chinese translation
-Change: Replace uses of fixed pixel metrics with

sizes based on the default font size

-Fix: CD ripper layout

new in 2.0.90 (2.1.0 rc1):
-Add: Hide main window when started with

--replaygain argument

-Add: Option to eject CD after ripping has been

completed (enabled by default)

-Add: New space holder for the "meta data" naming

mode that contains the source directory

-Add: Configuration options for cdparanoia
-Add: icedax ripper plugin
-Add: Copy album artist tags
-Change: Remember last folder for add

files/directory/playlist dialogs

-Change: Add symlinked files to file list