Fixed the problem on displaying icons.

Original one lead to a misbehavior on at least Chrome(Linux) and Firefox(Linux).

This problem is probable caused by forget to add 'glyphicon' to class for li.

The example on the [official bootstrap](http://getbootstrap.com/components/#glyphicons) site also have 'glyphicon' added to the class.

Before:
![err3](https://cloud.githubusercontent.com/assets/1883569/4539259/fc61d976-4dfa-11e4-944a-4b95d7438077.png)

After:
![err2](https://cloud.githubusercontent.com/assets/1883569/4539262/0055d0be-4dfb-11e4-8a49-4443eb207484.png)