Replace deprecated mpd lib

[sabl0r]

py-libmpdclient2 is deprecated.

This library is not maintained and has been superceded by the python-mpd library. New projects should use python-mpd. (http://incise.org/py-libmpdclient2.html)

But python-mpd is outdated, too.
Use python-mpd2 instead: https://github.com/Mic92/python-mpd2

[krmnn]

I know....
So, do we want a dependency that's not supported by debian testing?

[sabl0r]

Debian is always outdated. I ran into that problem, because py-libmpdclient2 isn't in gentoo portage anymore.
If we keep this dependency, it has to be configurable which plugins you want to use. Should not be difficult to implement @noyainrain?

[noyainrain]

I think, for the core and core plugins, we should only use libraries / dependencies that are supported from Debian stable to experimental (backward and forward compatability). It is reasonable to use Debian as reference, as it (and derivates) are widely used.

For optional plugins however, I don't care :) .

[noyainrain]

Tracked by #103 .