Release 0.3.4

Release date: 2019-11-08

API changes

• Rename out_fmt kwarg to fmt in show
• Add dpi kwarg to show
• Rename show function to render

New features

• Save rendered scores to image file using render
• Add wedge attribute to DynamicLoudnessMarkings to differentiate them
  from textual directions

Bug fixes

• Do not crash when calling time_signature_map on empty Part instances
• Fix bug in repeat unfolding