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
we only add script into erb file if it's absolute no alternative. This is not good, what if we need to render multiple code editor in one page ?