add bootstrap style to make the home page look better.

*add bootstrap style to make the home page look better.
*make the html code in index.php can ben maintainable.
*if the ui look better, i will try to update othe pages.
![ui](https://f.cloud.github.com/assets/2560415/2445473/dda37304-ae73-11e3-9020-7575eca9d6e8.jpg)