hit detection in grid/free mode.
rename function/class name.
rename function/class name.
refactor mvc.
use utility for hit detection.
apply state pattern.
implements item add function.
refactor toolbox(use mvc)
delete unused model.
modify view (move item/paint radio into toolbox)
add draw straight line option.
add draw straight line option
modify CanvasDrawer#drawText using fillText -> DOM
add connector draw tool.
rename 'paint' -> 'free line'
update html. some bug fix.
add property panel.
use knockout.js
Update README.md
ignore cell padding in non-grid mode.