Added TimeSigNote to insert TimeSig between notes.
Added support for time signature on the end of stave.
Added support for Canvas proxy.
Merge pull request #152 from panarch/master

Added support for time signature on the middle & end of stave.
Refactor canvas building in renderer.
Refactored rakefile.
Add support for stemmable tabnotes.

Also improve support for Caja environments.
Fix bug in beam font setting.
Update push script.
Scale numeric only.
Fix bug in BarNote, causing shifted lines.