Added function to show current Node.js version and new Bureau theme

I've added function `nvm_prompt_info()` that will show you current Node.js version wrapped in prefix and suffix. E.g.:
```bash
 %  ZSH_THEME_NVM_PROMPT_PREFIX="[ Node v"
 %  ZSH_THEME_NVM_PROMPT_SUFFIX=" ]"
 %  nvm_prompt_info
[ Node v0.10.15 ]
```
And added new Bureau theme:
![bureau](https://f.cloud.github.com/assets/529247/1503497/dc461f1c-48ab-11e3-922d-9897ee4f9cd2.png)