Immediate TODO list for text-engine:
 - Add basic input/editing capabilities
   - Keyboard shortcuts (Ctrl)
   - Unicode
 - Add style module
   - Line spacing
   - Bold, italic, underline
   - Colours
   - Cascades
   - Styles
   - CSS Importer?
 - Rich text content
   - Simple equations
   - Tables
   - Images
 - Rendering
   - Invalidation
   - Partial updates
   - Caching
 - Undo/redo system
   - Piece table data structure?
   - Operational transform?
