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.
Updated links.
Added donate button.
- Fixes Articulation and Annotation positioning for TabNotes
- Fixes Annotation overlap bugs for StaveNotes
- Added TabNote Articulation and Annotation tests
- Added Annotation justification test for StaveNote's with stems down
- Fixes bugs which breaks applyAndGetBeams for tabnotes
- Adds TabNote auto_stem functionality to normalize stem directions on beam creation
Fixed lint errors, some stem refactoring.
Only set stem direction for notes that have stems.
Factor out getYfor*Text into stemmables.
Vibratos should not overlap stems.
Add comment about tuplets.
Updated copyright in README.
Updated link in README.