Changing z-index to prevent cursor hidden fixes #19

Hi!, i found the hidden cursor problem inside tags. The problem was related
to the block cursor being overlapping by the tag background. 

![index html brackets 2013-12-21 18-31-56](https://f.cloud.github.com/assets/99183/1796761/23359ad0-6a88-11e3-95ac-c94d13269b38.png)