Allow line breaks in achievement descriptions (show as a list)

1.Now if there were any line breaks in the achievement description, it will show as a list.
2.Exsiting no line break ones will not be affected.

Screenshot:
![screen shot 2014-09-03 at 11 40 58 am](https://cloud.githubusercontent.com/assets/4983239/4129270/8060c146-331c-11e4-82ab-cbe6e4e2fed9.png)