use param mycanvas

global param 'mycanvas' can't delete
Update LLpractice.js
modularity LLpractice.js and fix some issues

package params and functions,only provide useful API

You may use in index file like this:
LLpractice.init('hitmaps/xueyuehua.json','bgm/xueyuehua.json');
LLpractice.resize();
LLpractice.start();
Merge pull request #2 from MagicJuly/master

modularity LLpractice.js and fix some issues