Add preprocessor and changes in commands

I know that you want to avoid this and so do I but just to have the job done.

## How to use

~~~
$ make
~~~

It will rewrite the `*.tex` files adding the `\begin{VerbGroup}` and `\end{VerbGroup}` when needed. After rewrite the files it will call `pdflatex`.

![pdf](https://cloud.githubusercontent.com/assets/1506457/3349268/ffca96b0-f95a-11e3-9056-b0c499722c12.png)

## Build Issue

If you run `make` twice it will add `\begin{VerbGroup}` and `\end{VerbGroup}` twice. I don't want to add the `VerbGroup` manually but didn't thought in a good way to create an temporary directory for the build.

## Replace `fancyvrb` with `listings`

I couldn't find how to control the vertical space before and after `fancyvrb` environments. Because of it I **partially** replace it with `listings` environment.