auto restore last attempt training

![screen shot 2014-09-07 at 22 55 35](https://cloud.githubusercontent.com/assets/4983239/4178625/2f710756-369f-11e4-837b-8bb14d17017b.png)

1. If a student haven't done a coding question, his code will be saved and auto restore next time.

2.provide a button if he wants to revert to the template code

3.UI is not beautiful.. need improve
if you can fix it at 0, then it means it's useless isn't it? remove it please.