remove unused library
forbid new reward overlap with old ones
clean code step 1
clean code;
remove leave player from list
Merge branch 'yiweili' of https://github.com/yutongp/RaiseMeUp into ypei

Conflicts:
	client/code/app/game_client.js
clean code
Merge branch 'yifei' of https://github.com/yutongp/RaiseMeUp into yifei

Conflicts:
	client/code/app/entry.js
	client/views/game.html
Merge branch 'yifei' of https://github.com/yutongp/RaiseMeUp into ypei
bck_music, movement eat_coin sound added
 ai added
Merge branch 'yifei' of https://github.com/yutongp/RaiseMeUp into ypei

Conflicts:
	client/code/app/game_client.js
Merge branch 'lucas' of https://github.com/yutongp/RaiseMeUp into ypei

Conflicts:
	client/code/app/game_client.js
add threejs in local path
code clean tri!!!
fix bug in validPosition that always return True
solve the problem of click out of bound object