Implemented Clef.named_pitch_to_staff_position().

Example:

    >>> staff = Staff("c'8 d'8 e'8 f'8 g'8 a'8 b'8 c''8")
    >>> clef = Clef('treble')
    >>> for note in staff:
    ...     named_pitch = note.written_pitch
    ...     staff_position = clef.named_pitch_to_staff_position(named_pitch)
    ...     message = '{}\t{!s}'
    ...     message = message.format(named_pitch, staff_position)
    ...     print(message)
    c'      StaffPosition(-6)
    d'      StaffPosition(-5)
    e'      StaffPosition(-4)
    f'      StaffPosition(-3)
    g'      StaffPosition(-2)
    a'      StaffPosition(-1)
    b'      StaffPosition(0)
    c''     StaffPosition(1)

Deprecated pitchtools.named_pitch_and_clef_to_staff_position_number().

Use Clef.named_pitch_to_staff_position() instead.