优化拖动检测
完善拖动的碰撞检测
完善画布操作
层模块化
修改Line类，fix bug
Merge branch 'jack' of https://github.com/lln7777/zhuyun into jack

Conflicts:
	public/javascripts/funcs.coffee
	public/javascripts/funcs.js
	public/javascripts/global.coffee
	public/javascripts/global.js
	public/javascripts/index.js
	views/index.ejs
 Merge branch 'jack' of https://github.com/lln7777/zhuyun into sx

Conflicts:
	public/javascripts/components.coffee
	public/javascripts/components.js
	public/javascripts/funcs.coffee
	public/javascripts/funcs.js
	public/javascripts/global.coffee
	public/javascripts/index.js
去掉画直线的文字