Fixed Issue #7 & lilypond_notation bug & tabs/spaces mixture 

Hello Gonzalo, 
I finally traced the Exception of my issue #7 down to the source: The assignment of new_note_tone is falsely set to C instead of B. I quickly hacked some ugly workaround for this case, maybe you find something more beautiful? Besides the tabs & spaces mixture I also fixed a permutation bug in the lilypond_notation method.
All tests ran fine, please let me know if you don't agree with some of my changes.
Best wishes
Marco