prevents the html body from dancing

This update get body scrollbar width, and add corresponding width to fixed elements and body`s margin right.

![image](https://f.cloud.github.com/assets/3171104/963638/e0f89208-0506-11e3-9eb9-0e499791f433.png)

![image](https://f.cloud.github.com/assets/3171104/963640/ea3f8bd2-0506-11e3-94d2-f8cf0de7e309.png)