Adds support for new content types and fixes an error with the text-input mode.
Adds support for new content types and fixes an error with the text-input mode.

New:
- removing Group now possible by pressing the delete-key
- in Browsers supporting the File API (latest Firefox and Chrome) 
  embedding images can be done by dragging them on the canvas
Fix:
- Keypress on a selected textgroup now inserts the right character.
Moerphy/dizzy.js