Displaying A# instead of Bb in the key of C

[santiagobarros]

> Transposer.transpose('C Bb').fromKey('C').toKey('C').toString();
'C A#'
> Transposer.transpose('C A#').fromKey('C').toKey('C').toString();
'C A#'
> Transposer.transpose('C A#').fromKey('F').toKey('F').toString();
'C Bb'
> Transposer.transpose('C Bb').fromKey('F').toKey('F').toString();
'C Bb'

In the key of C, the chord should be displayed as Bb. The script does a good job for the key of F