Handbell Hero 0.5.0

• Added visual metronome which can be toggled with "M" key
• Better handle unassigned notes
• Notes can be explicitly "emphasized" in songs. When authoring songs, use '>' to turn on note emphasis and '<' to turn it off. If this is used, emphasized notes will be drawn with empty circles, while un-emphasized notes will be drawn with filled circles.
• Songs can set the "beat length", which is the distance the song will move each time it is scrolled to the left or the right. For example, !beatlength 8 will move it by a quarter note each time (which is the default).