Add the 'debug' switch
Add another argument to the 'Scribble' constructor to be able to turn
console logs on/off

Signed-off-by: Mario Kozjak <kozjakm1@gmail.com>
Added track duration to NowPlaying. Fixes #1
The 'duration' property in 'song' is optional.
Note that 'make install' fails on that one, although the feature
actually works.  Maybe the test needs to be modified?

Signed-off-by: Mario Kozjak <kozjakm1@gmail.com>